# 4.20.3 Immediately fails to package: System.ArgumentNullException: Value cannot be null

**URL:** <https://forums.unrealengine.com/t/4-20-3-immediately-fails-to-package-system-argumentnullexception-value-cannot-be-null/436383>\
**Category:** Blueprint\
**Tags:** error, unreal-engine, fail, Packaging, Blueprint, question\
**Created:** [October 26, 2018, 11:46am UTC](https://forums.unrealengine.com/t/4-20-3-immediately-fails-to-package-system-argumentnullexception-value-cannot-be-null/436383 "2018-10-26T11:46:22Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![iamisandisnt](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@iamisandisnt](https://forums.unrealengine.com/u/iamisandisnt)\
**Post date:** [October 26, 2018, 11:46am UTC](https://forums.unrealengine.com/t/4-20-3-immediately-fails-to-package-system-argumentnullexception-value-cannot-be-null/436383/1 "2018-10-26T11:46:22Z")

</div>

Cleaned up all the errors and warnings in my log but this happens right off the bat when I go to package.

I recently moved to a new computer and copied my project file over. I installed the same version of Visual Studio 2015 Update 3 and have all the components necessary.

I’ve deleted my derived data cache, intermediate and saved folders.

Running from a blueprint-only project straight from the EPIC launcher. Packing worked not too long ago but I can’t recall what version.

Looks like this specific problem has been cropping up in other 4.20 packaging attempts I’ve seen but only as a question in a couple of places, couldn’t find any discussion on it:

\<\>c.b\_\_4\_0: ERROR: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. —\> System.ArgumentNullException: Value cannot be null.

Full log:

Automation.ParseCommandLine: Parsing command line: -ScriptsForProject=“C:/Users/user/Documents/Unreal Projects/TheFreeLands 4.20/TheFeyLands.uproject” BuildCookRun -nocompile -nocompileeditor -installed -nop4 -project=“C:/Users/user/Documents/Unreal Projects/TheFreeLands 4.20/TheFeyLands.uproject” -cook -stage -archive -archivedirectory=C:/Users/user/Documents/Unreal/Exports/TestExportAlpha6 -package -clientconfig=Development -ue4exe=UE4Editor-Cmd.exe -clean -compressed -pak -prereqs -nodebuginfo -targetplatform=Win64 -build -utf8output  
Automation.Process: Setting up command environment.  
InternalUtils.SafeFileExists: SafeFileExists C:\Program Files\Epic Games\UE\_4.20\Engine\Binaries\DotNET\AutomationTool.exe=True  
InternalUtils.GetEnvironmentVariable: GetEnvironmentVariable uebp\_LOCAL\_ROOT=  
InternalUtils.GetEnvironmentVariable: GetEnvironmentVariable uebp\_LOCAL\_ROOT=  
InternalUtils.GetEnvironmentVariable: GetEnvironmentVariable uebp\_EngineSavedFolder=  
CommandUtils.SetEnvVar: SetEnvVar uebp\_EngineSavedFolder=C:/Program Files/Epic Games/UE\_4.20/Engine/Programs/AutomationTool/Saved  
InternalUtils.GetEnvironmentVariable: GetEnvironmentVariable uebp\_EngineSavedFolder=C:/Program Files/Epic Games/UE\_4.20/Engine/Programs/AutomationTool/Saved  
InternalUtils.GetEnvironmentVariable: GetEnvironmentVariable uebp\_CSVFile=  
InternalUtils.GetEnvironmentVariable: GetEnvironmentVariable uebp\_LogFolder=  
InternalUtils.GetEnvironmentVariable: GetEnvironmentVariable uebp\_LOCAL\_ROOT=C:/Program Files/Epic Games/UE\_4.20  
CommandUtils.SetEnvVar: SetEnvVar uebp\_LogFolder=C:/Users/user/AppData/Roaming/Unreal Engine/AutomationTool/Logs/C+Program+Files+Epic+Games+UE\_4.20  
InternalUtils.SafeDeleteFile: SafeDeleteFile C:\Users\user\AppData\Roaming\Unreal Engine\AutomationTool\Logs\C+Program+Files+Epic+Games+UE\_4.20\Log.txt  
InternalUtils.GetEnvironmentVariable: GetEnvironmentVariable uebp\_FinalLogFolder=  
CommandUtils.SetEnvVar: SetEnvVar uebp\_FinalLogFolder=C:/Users/user/AppData/Roaming/Unreal Engine/AutomationTool/Logs/C+Program+Files+Epic+Games+UE\_4.20  
InternalUtils.SafeFileExists: SafeFileExists C:\WINDOWS\system32\robocopy.exe=True  
InternalUtils.SafeFileExists: SafeFileExists C:\WINDOWS\system32\mount.exe=False  
InternalUtils.SafeFileExists: SafeFileExists C:\WINDOWS\Sysnative\mount.exe=False  
InternalUtils.SafeFileExists: SafeFileExists C:\WINDOWS\system32\cmd.exe=True  
CommandUtils.SetEnvVar: SetEnvVar MallocNanoZone=0  
InternalUtils.GetEnvironmentVariable: GetEnvironmentVariable uebp\_UATChildInstance=0  
InternalUtils.SafeDeleteFile: SafeDeleteFile C:\Users\user\AppData\Local\Temp\UAT\C+Program+Files+Epic+Games+UE\_4.20\Rules\UATRules1750363209.dll  
InternalUtils.SafeDeleteFile: SafeDeleteFile C:\Users\user\AppData\Local\Temp\UAT\C+Program+Files+Epic+Games+UE\_4.20\Rules\UATRules1750363209.pdb  
InternalUtils.SafeDeleteFile: SafeDeleteFile C:\Users\user\AppData\Local\Temp\UAT\C+Program+Files+Epic+Games+UE\_4.20\Rules\UATRules1750363209SourceFiles.txt  
InternalUtils.SafeFileExists: SafeFileExists C:\Users\user\Documents\Unreal Projects\TheFreeLands 4.20\TheFeyLands.uproject=True  
InternalUtils.SafeFileExists: SafeFileExists C:\Users\user\Documents\Unreal Projects\TheFreeLands 4.20\TheFeyLands.uproject=True  
BuildCookRun.SetupParams: Setting up ProjectParams for C:\Users\user\Documents\Unreal Projects\TheFreeLands 4.20\TheFeyLands.uproject  
InternalUtils.SafeFileExists: SafeFileExists C:\Users\user\AppData\Local\Temp\UAT\C+Program+Files+Epic+Games+UE\_4.20\Rules\UATRules1750363209.dll=False  
\<\>c.b\_\_4\_1: ==============================================================================  
\<\>c.b\_\_4\_0: ERROR: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. —\> System.ArgumentNullException: Value cannot be null.  
\<\>c.b\_\_4\_0: Parameter name: source  
\<\>c.b\_\_4\_0: at System.Linq.Enumerable.Select[TSource,TResult](IEnumerable`1 source, Func`2 selector)  
\<\>c.b\_\_4\_0: at UnrealBuildTool.TargetRules.FormatHexBytes(Byte[] Data) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\TargetRules.cs:line 1255  
\<\>c.b\_\_4\_0: at UnrealBuildTool.TargetRules…ctor(TargetInfo Target) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\TargetRules.cs:line 1231  
\<\>c.b\_\_4\_0: at TheFeyLandsTarget…ctor(TargetInfo Target) in c:\Users\user\Documents\Unreal Projects\TheFreeLands 4.20\Intermediate\Source\TheFeyLands.Target.cs:line 7  
\<\>c.b\_\_4\_0: — End of inner exception stack trace —  
\<\>c.b\_\_4\_0: at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)  
\<\>c.b\_\_4\_0: at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)  
\<\>c.b\_\_4\_0: at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, StackCrawlMark& stackMark)  
\<\>c.b\_\_4\_0: at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)  
\<\>c.b\_\_4\_0: at System.Activator.CreateInstance(Type type, Object[] args)  
\<\>c.b\_\_4\_0: at AutomationTool.ProjectUtils.CompileAndLoadTargetsAssembly(ProjectProperties Properties, FileReference TargetsDllFilename, Boolean DoNotCompile, List`1 TargetScripts) in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\ProjectUtils.cs:line 570 <>c.b__4_0: at AutomationTool.ProjectUtils.DetectTargetsForProject(ProjectProperties Properties, List`1 ExtraSearchPaths) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\ProjectUtils.cs:line 533  
\<\>c.b\_\_4\_0: at AutomationTool.ProjectUtils.DetectProjectProperties(FileReference RawProjectPath, List`1 ClientTargetPlatforms, List`1 ClientTargetConfigurations, Boolean AssetNativizationRequested) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\ProjectUtils.cs:line 348  
\<\>c.b\_\_4\_0: at AutomationTool.ProjectUtils.GetProjectProperties(FileReference RawProjectPath, List`1 ClientTargetPlatforms, List`1 ClientTargetConfigurations, Boolean AssetNativizationRequested) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\ProjectUtils.cs:line 99  
\<\>c.b\_\_4\_0: at AutomationTool.ProjectParams.AutodetectSettings(Boolean bReset) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\ProjectParams.cs:line 1944  
\<\>c.b\_\_4\_0: at AutomationTool.ProjectParams…ctor(FileReference RawProjectPath, BuildCommand Command, String Device, String MapToRun, String AdditionalServerMapParams, ParamList`1 Port, String RunCommandline, String StageCommandline, String BundleName, String StageDirectoryParam, String UE4Exe, String SignPak, List`1 ClientConfigsToBuild, List`1 ServerConfigsToBuild, ParamList`1 MapsToCook, ParamList`1 MapIniSectionsToCook, ParamList`1 DirectoriesToCook, String InternationalizationPreset, ParamList`1 CulturesToCook, ParamList`1 ClientCookedTargets, ParamList`1 EditorTargets, ParamList`1 ServerCookedTargets, List`1 ClientTargetPlatforms, Dictionary`2 ClientDependentPlatformMap, List`1 ServerTargetPlatforms, Dictionary`2 ServerDependentPlatformMap, Nullable`1 Build, Nullable`1 SkipBuildClient, Nullable`1 SkipBuildEditor, Nullable`1 Cook, Nullable`1 Run, Nullable`1 SkipServer, Nullable`1 Clean, Nullable`1 Compressed, String AdditionalPakOptions, Nullable`1 UseDebugParamForEditorExe, Nullable`1 IterativeCooking, String IterateSharedCookedBuild, Nullable`1 IterateSharedBuildUsePrecompiledExe, Nullable`1 CookAll, Nullable`1 CookPartialGC, Nullable`1 CookInEditor, String CookOutputDir, Nullable`1 CookMapsOnly, Nullable`1 CookOnTheFly, Nullable`1 CookOnTheFlyStreaming, Nullable`1 UnversionedCookedContent, Nullable`1 EncryptIniFiles, Nullable`1 EncryptPakIndex, Nullable`1 EncryptEverything, Nullable`1 SkipCookingEditorContent, Nullable`1 NumCookersToSpawn, String AdditionalCookerOptions, String BasedOnReleaseVersion, String CreateReleaseVersion, String CreateReleaseVersionBasePath, String BasedOnReleaseVersionBasePath, Nullable`1 GeneratePatch, Nullable`1 AddPatchLevel, Nullable`1 StageBaseReleasePaks, Nullable`1 GenerateRemaster, String DiscVersion, String DLCName, String DiffCookedContentPath, Nullable`1 DLCIncludeEngineContent, Nullable`1 DLCPakPluginFile, Nullable`1 DLCActLikePatch, Nullable`1 CrashReporter, Nullable`1 DedicatedServer, Nullable`1 Client, Nullable`1 Deploy, String DeployFolder, String GetFile, Nullable`1 FileServer, Nullable`1 Foreign, Nullable`1 ForeignCode, Nullable`1 LogWindow, Nullable`1 NoCleanStage, Nullable`1 NoClient, Nullable`1 NoDebugInfo, Nullable`1 SeparateDebugInfo, Nullable`1 MapFile, Nullable`1 NoXGE, Nullable`1 Package, Nullable`1 Pak, Nullable`1 Prereqs, String AppLocalDirectory, Nullable`1 NoBootstrapExe, Nullable`1 SignedPak, Nullable`1 NullRHI, Nullable`1 FakeClient, Nullable`1 EditorTest, Nullable`1 RunAutomationTests, String RunAutomationTest, Nullable`1 CrashIndex, Nullable`1 SkipCook, Nullable`1 SkipCookOnTheFly, Nullable`1 SkipPak, Nullable`1 PrePak, Nullable`1 SkipStage, Nullable`1 Stage, Nullable`1 Manifests, Nullable`1 CreateChunkInstall, Nullable`1 Unattended, Nullable`1 NumClients, Nullable`1 Archive, String ArchiveDirectoryParam, Nullable`1 ArchiveMetaData, Nullable`1 CreateAppBundle, ParamList`1 ProgramTargets, Nullable`1 Distribution, Nullable`1 Prebuilt, Nullable`1 RunTimeoutSeconds, String SpecifiedArchitecture, String UbtArgs, Nullable`1 IterativeDeploy, Nullable`1 FastCook, Nullable`1 IgnoreCookErrors, Nullable`1 RunAssetNativization, Nullable`1 CodeSign, Nullable`1 TreatNonShippingBinariesAsDebugFiles, Nullable`1 UseExtraFlavor, String Provision, String Certificate, String Team, Boolean AutomaticSigning, ParamList`1 InMapsToRebuildLightMaps, ParamList`1 InMapsToRebuildHLOD, ParamList`1 TitleID) in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\ProjectParams.cs:line 1019 <>c.b__4_0: at BuildCookRun.SetupParams() in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\Scripts\BuildCookRun.Automation.cs:line 52 <>c.b__4_0: at BuildCookRun.ExecuteBuild() in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\Scripts\BuildCookRun.Automation.cs:line 39 <>c.b__4_0: at AutomationTool.BuildCommand.Execute() in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\BuildCommand.cs:line 112 <>c.b__4_0: at AutomationTool.Automation.Execute(List`1 CommandsToExecute, Dictionary`2 Commands) in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\Automation.cs:line 562 <>c.b__4_0: at AutomationTool.Automation.Process(String[] Arguments, StartupTraceListener StartupListener) in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\Automation.cs:line 532 <>c.b__4_0: at AutomationTool.Program.MainProc(String[] Arguments, StartupTraceListener StartupListener) in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\Program.cs:line 174 <>c.b __4_0: at AutomationTool.Program.<>c__ DisplayClass1_0.b__0() in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\Program.cs:line 100 <>c.b__4_0: at AutomationTool.InternalUtils.RunSingleInstance(Func`1 Main) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\Utils.cs:line 725  
\<\>c.b\_\_4\_0: at AutomationTool.Program.Main() in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\Program.cs:line 100  
\<\>c.b\_\_4\_0: (see C:\Users\user\AppData\Roaming\Unreal Engine\AutomationTool\Logs\C+Program+Files+Epic+Games+UE\_4.20\Log.txt for full exception trace)  
\<\>c.b\_\_4\_1:  
\<\>c.b\_\_4\_1: ArgumentNullException: Value cannot be null.  
\<\>c.b\_\_4\_1: Parameter name: source  
\<\>c.b\_\_4\_1: at System.Linq.Enumerable.Select[TSource,TResult](IEnumerable`1 source, Func`2 selector)  
\<\>c.b\_\_4\_1: at UnrealBuildTool.TargetRules.FormatHexBytes(Byte[] Data) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\TargetRules.cs:line 1255  
\<\>c.b\_\_4\_1: at UnrealBuildTool.TargetRules…ctor(TargetInfo Target) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Configuration\TargetRules.cs:line 1231  
\<\>c.b\_\_4\_1: at TheFeyLandsTarget…ctor(TargetInfo Target) in c:\Users\user\Documents\Unreal Projects\TheFreeLands 4.20\Intermediate\Source\TheFeyLands.Target.cs:line 7  
\<\>c.b\_\_4\_1: Wrapped by TargetInvocationException: Exception has been thrown by the target of an invocation.  
\<\>c.b\_\_4\_1: at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)  
\<\>c.b\_\_4\_1: at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)  
\<\>c.b\_\_4\_1: at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, StackCrawlMark& stackMark)  
\<\>c.b\_\_4\_1: at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)  
\<\>c.b\_\_4\_1: at System.Activator.CreateInstance(Type type, Object[] args)  
\<\>c.b\_\_4\_1: at AutomationTool.ProjectUtils.CompileAndLoadTargetsAssembly(ProjectProperties Properties, FileReference TargetsDllFilename, Boolean DoNotCompile, List`1 TargetScripts) in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\ProjectUtils.cs:line 570 <>c.b__4_1: at AutomationTool.ProjectUtils.DetectTargetsForProject(ProjectProperties Properties, List`1 ExtraSearchPaths) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\ProjectUtils.cs:line 533  
\<\>c.b\_\_4\_1: at AutomationTool.ProjectUtils.DetectProjectProperties(FileReference RawProjectPath, List`1 ClientTargetPlatforms, List`1 ClientTargetConfigurations, Boolean AssetNativizationRequested) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\ProjectUtils.cs:line 348  
\<\>c.b\_\_4\_1: at AutomationTool.ProjectUtils.GetProjectProperties(FileReference RawProjectPath, List`1 ClientTargetPlatforms, List`1 ClientTargetConfigurations, Boolean AssetNativizationRequested) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\ProjectUtils.cs:line 99  
\<\>c.b\_\_4\_1: at AutomationTool.ProjectParams.AutodetectSettings(Boolean bReset) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\ProjectParams.cs:line 1944  
\<\>c.b\_\_4\_1: at AutomationTool.ProjectParams…ctor(FileReference RawProjectPath, BuildCommand Command, String Device, String MapToRun, String AdditionalServerMapParams, ParamList`1 Port, String RunCommandline, String StageCommandline, String BundleName, String StageDirectoryParam, String UE4Exe, String SignPak, List`1 ClientConfigsToBuild, List`1 ServerConfigsToBuild, ParamList`1 MapsToCook, ParamList`1 MapIniSectionsToCook, ParamList`1 DirectoriesToCook, String InternationalizationPreset, ParamList`1 CulturesToCook, ParamList`1 ClientCookedTargets, ParamList`1 EditorTargets, ParamList`1 ServerCookedTargets, List`1 ClientTargetPlatforms, Dictionary`2 ClientDependentPlatformMap, List`1 ServerTargetPlatforms, Dictionary`2 ServerDependentPlatformMap, Nullable`1 Build, Nullable`1 SkipBuildClient, Nullable`1 SkipBuildEditor, Nullable`1 Cook, Nullable`1 Run, Nullable`1 SkipServer, Nullable`1 Clean, Nullable`1 Compressed, String AdditionalPakOptions, Nullable`1 UseDebugParamForEditorExe, Nullable`1 IterativeCooking, String IterateSharedCookedBuild, Nullable`1 IterateSharedBuildUsePrecompiledExe, Nullable`1 CookAll, Nullable`1 CookPartialGC, Nullable`1 CookInEditor, String CookOutputDir, Nullable`1 CookMapsOnly, Nullable`1 CookOnTheFly, Nullable`1 CookOnTheFlyStreaming, Nullable`1 UnversionedCookedContent, Nullable`1 EncryptIniFiles, Nullable`1 EncryptPakIndex, Nullable`1 EncryptEverything, Nullable`1 SkipCookingEditorContent, Nullable`1 NumCookersToSpawn, String AdditionalCookerOptions, String BasedOnReleaseVersion, String CreateReleaseVersion, String CreateReleaseVersionBasePath, String BasedOnReleaseVersionBasePath, Nullable`1 GeneratePatch, Nullable`1 AddPatchLevel, Nullable`1 StageBaseReleasePaks, Nullable`1 GenerateRemaster, String DiscVersion, String DLCName, String DiffCookedContentPath, Nullable`1 DLCIncludeEngineContent, Nullable`1 DLCPakPluginFile, Nullable`1 DLCActLikePatch, Nullable`1 CrashReporter, Nullable`1 DedicatedServer, Nullable`1 Client, Nullable`1 Deploy, String DeployFolder, String GetFile, Nullable`1 FileServer, Nullable`1 Foreign, Nullable`1 ForeignCode, Nullable`1 LogWindow, Nullable`1 NoCleanStage, Nullable`1 NoClient, Nullable`1 NoDebugInfo, Nullable`1 SeparateDebugInfo, Nullable`1 MapFile, Nullable`1 NoXGE, Nullable`1 Package, Nullable`1 Pak, Nullable`1 Prereqs, String AppLocalDirectory, Nullable`1 NoBootstrapExe, Nullable`1 SignedPak, Nullable`1 NullRHI, Nullable`1 FakeClient, Nullable`1 EditorTest, Nullable`1 RunAutomationTests, String RunAutomationTest, Nullable`1 CrashIndex, Nullable`1 SkipCook, Nullable`1 SkipCookOnTheFly, Nullable`1 SkipPak, Nullable`1 PrePak, Nullable`1 SkipStage, Nullable`1 Stage, Nullable`1 Manifests, Nullable`1 CreateChunkInstall, Nullable`1 Unattended, Nullable`1 NumClients, Nullable`1 Archive, String ArchiveDirectoryParam, Nullable`1 ArchiveMetaData, Nullable`1 CreateAppBundle, ParamList`1 ProgramTargets, Nullable`1 Distribution, Nullable`1 Prebuilt, Nullable`1 RunTimeoutSeconds, String SpecifiedArchitecture, String UbtArgs, Nullable`1 IterativeDeploy, Nullable`1 FastCook, Nullable`1 IgnoreCookErrors, Nullable`1 RunAssetNativization, Nullable`1 CodeSign, Nullable`1 TreatNonShippingBinariesAsDebugFiles, Nullable`1 UseExtraFlavor, String Provision, String Certificate, String Team, Boolean AutomaticSigning, ParamList`1 InMapsToRebuildLightMaps, ParamList`1 InMapsToRebuildHLOD, ParamList`1 TitleID) in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\ProjectParams.cs:line 1019 <>c.b__4_1: at BuildCookRun.SetupParams() in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\Scripts\BuildCookRun.Automation.cs:line 52 <>c.b__4_1: at BuildCookRun.ExecuteBuild() in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\Scripts\BuildCookRun.Automation.cs:line 39 <>c.b__4_1: at AutomationTool.BuildCommand.Execute() in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\BuildCommand.cs:line 112 <>c.b__4_1: at AutomationTool.Automation.Execute(List`1 CommandsToExecute, Dictionary`2 Commands) in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\Automation.cs:line 562 <>c.b__4_1: at AutomationTool.Automation.Process(String[] Arguments, StartupTraceListener StartupListener) in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\Automation.cs:line 532 <>c.b__4_1: at AutomationTool.Program.MainProc(String[] Arguments, StartupTraceListener StartupListener) in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\Program.cs:line 174 <>c.b __4_1: at AutomationTool.Program.<>c__ DisplayClass1_0.b__0() in D:\Build\++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\Program.cs:line 100 <>c.b__4_1: at AutomationTool.InternalUtils.RunSingleInstance(Func`1 Main) in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\AutomationUtils\Utils.cs:line 725  
\<\>c.b\_\_4\_1: at AutomationTool.Program.Main() in D:\Build++UE4\Sync\Saved\CsTools\Engine\Source\Programs\AutomationTool\Program.cs:line 100  
\<\>c.b\_\_4\_1: ==============================================================================  
Program.Main: AutomationTool exiting with ExitCode=1 (Error\_Unknown)

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<div class="post-metadata">

**Author:** ![iamisandisnt](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@iamisandisnt](https://forums.unrealengine.com/u/iamisandisnt)\
**Post date:** [October 26, 2018, 1:56pm UTC](https://forums.unrealengine.com/t/4-20-3-immediately-fails-to-package-system-argumentnullexception-value-cannot-be-null/436383/2 "2018-10-26T13:56:27Z")

</div>

FIXED!

Friendly suggestion from a follower: uncheck encryption check boxes in the Crypto section of Project Settings!