Microsoft.MakeFile.targets(45, 5): [MSB3073] exited with code 6. error

Hello everyone,

I am receiving the following error on when trying to build a fresh game with UE5 using Rider. I was receiving the same error when using VS2019 with UE4.26. I have done some research online regarding the error and what others that used to troubleshoot, but I am still at a loss to determine how to fix the error.

Any help provided would be tremendously helpful and I know would help others in the community.



I was having issues with UE5.0 source build so I deleted and re-downloaded UE5 Early Access. Getting this same error now when trying to build my Project I started with 5.0

1 Like

Did you find a solution?

Have you found a solution to this?

I had the same error. Resolved with checking in the project the last changes i’ve made and actually i wrongly used “UFUNCTION(Server, Reliable)”. hope this helps

Had the same error.
It was because I installed RiderLink plugin as a UE5’s engine plugin. Apprently RiderLink preview has a bug, and it only works as a per-project plugin.
Removed the RiderLink folder from UE5’s engine plugin (Plugin/Developer/RiderLink) and reinstalled it in the project folder. And the project was finally built.

More here: Unreal Engine 5 - Jetbrains Rider Early Access - YouTube


Had a similar error and the issue was a file that Rider was trying to write to that was not checked out in Perforce and thus read-only on disk.

Rider somewhat unhelpfully collapses the error log into just that message, but you can expand it with a button on the left.


I believe that found the problem, if the Live Coding configuration of integration is enable in your Unreal Engine 5, can be this that are creating the conflict of Mutex :eyes:

Try disable the Live Coding or press Ctrl+Alt+F11 in the editor(VS2022) or game, and try compile again.

This information are in a log file from Unreal Engine 5 in:


See below the complete message:

Checking for live coding mutex: Global\LiveCoding_D++Epic Games+UE_5.1+Engine+Binaries+Win64+UnrealEditor.exe
Unable to build while Live Coding is active. Exit the editor and game, or press Ctrl+Alt+F11 if iterating on code in the editor or game
BuildException: Unable to build while Live Coding is active. Exit the editor and game, or press Ctrl+Alt+F11 if iterating on code in the editor or game
at UnrealBuildTool.HotReload.CheckForLiveCodingSessionActive(TargetDescriptor TargetDescriptor, TargetMakefile Makefile, BuildConfiguration BuildConfiguration, ILogger Logger) in D:\build++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\System\HotReload.cs:line 231
at UnrealBuildTool.BuildMode.Build(TargetMakefile[] Makefiles, List`1 TargetDescriptors, BuildConfiguration BuildConfiguration, BuildOptions Options, FileReference WriteOutdatedActionsFile, ILogger Logger) in D:\build++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Modes\BuildMode.cs:line 526
at UnrealBuildTool.BuildMode.Execute(CommandLineArguments Arguments, ILogger Logger) in D:\build++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\Modes\BuildMode.cs:line 242
at UnrealBuildTool.UnrealBuildTool.Main(String[] ArgumentsArray) in D:\build++UE5\Sync\Engine\Saved\CsTools\Engine\Source\Programs\UnrealBuildTool\UnrealBuildTool.cs:line 648
WriteFileIfChanged() wrote 0 changed files of 0 requested writes.

have many more informations, but are personal information from my project and path from ssd :smile: