I am facing the same issue and am unable to access the build. I have also updated the FAB plugin, but it is still not functioning. Please share the output log.
UATHelper: Packaging (Windows): LogWindows: Error: appError called: Assertion failed: CurrentApplication.IsValid() [File:D:\build++UE5\Sync\LocalInstall\Engine\Source\Runtime\Slate\Public\Framework\Application\SlateApplication.h] [Line: 255]
UATHelper: Packaging (Windows): LogWindows: Error: begin: stack for UAT
UATHelper: Packaging (Windows): LogWindows: Error: === Critical error: ===
UATHelper: Packaging (Windows): LogWindows: Error:
UATHelper: Packaging (Windows): LogWindows: Error: Assertion failed: CurrentApplication.IsValid() [File:D:\build++UE5\Sync\LocalInstall\Engine\Source\Runtime\Slate\Public\Framework\Application\SlateApplication.h] [Line: 255]
UATHelper: Packaging (Windows): LogWindows: Error:
UATHelper: Packaging (Windows): LogWindows: Error:
UATHelper: Packaging (Windows): LogWindows: Error:
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x000002236608ad96 UnrealEditor-Fab.dll!FFabBrowser::RegisterSlateStyle() [D:\build++UE5\Sync\LocalBuilds\Fab\0.0.1\HostProject\Plugins\Fab\Source\Fab\Private\FabBrowser.cpp:98]
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x000002236609725a UnrealEditor-Fab.dll!FFabModule::StartupModule() [D:\build++UE5\Sync\LocalBuilds\Fab\0.0.1\HostProject\Plugins\Fab\Source\Fab\Private\FabModule.cpp:35]
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007fff1d305954 UnrealEditor-Core.dll!UnknownFunction
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007fffc3d987ee UnrealEditor-Projects.dll!UnknownFunction
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007fffc3db56c3 UnrealEditor-Projects.dll!UnknownFunction
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007fffc3d9801a UnrealEditor-Projects.dll!UnknownFunction
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ff60c632591 UnrealEditor-Cmd.exe!UnknownFunction
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ff60c63634f UnrealEditor-Cmd.exe!UnknownFunction
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ff60c62cfb6 UnrealEditor-Cmd.exe!UnknownFunction
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ff60c62d37a UnrealEditor-Cmd.exe!UnknownFunction
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ff60c630854 UnrealEditor-Cmd.exe!UnknownFunction
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ff60c646984 UnrealEditor-Cmd.exe!UnknownFunction
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007ff60c648eb6 UnrealEditor-Cmd.exe!UnknownFunction
UATHelper: Packaging (Windows): LogWindows: Error: [Callstack] 0x00007fffe0617374 KERNEL32.DLL!UnknownFunction
UATHelper: Packaging (Windows): LogWindows: Error:
UATHelper: Packaging (Windows): LogWindows: Error: end: stack for UAT
PackagingResults: Error: appError called: Assertion failed: CurrentApplication.IsValid() [File:D:\build++UE5\Sync\LocalInstall\Engine\Source\Runtime\Slate\Public\Framework\Application\SlateApplication.h] [Line: 255]
PackagingResults: Error: begin: stack for UAT
PackagingResults: Error: === Critical error: ===
PackagingResults: Error: Assertion failed: CurrentApplication.IsValid() [File:D:\build++UE5\Sync\LocalInstall\Engine\Source\Runtime\Slate\Public\Framework\Application\SlateApplication.h] [Line: 255]
PackagingResults: Error: [Callstack] 0x000002236608ad96 UnrealEditor-Fab.dll!FFabBrowser::RegisterSlateStyle() [D:\build++UE5\Sync\LocalBuilds\Fab\0.0.1\HostProject\Plugins\Fab\Source\Fab\Private\FabBrowser.cpp:98]
PackagingResults: Error: [Callstack] 0x000002236609725a UnrealEditor-Fab.dll!FFabModule::StartupModule() [D:\build++UE5\Sync\LocalBuilds\Fab\0.0.1\HostProject\Plugins\Fab\Source\Fab\Private\FabModule.cpp:35]
PackagingResults: Error: [Callstack] 0x00007fff1d305954 UnrealEditor-Core.dll!UnknownFunction
PackagingResults: Error: [Callstack] 0x00007fffc3d987ee UnrealEditor-Projects.dll!UnknownFunction
PackagingResults: Error: [Callstack] 0x00007fffc3db56c3 UnrealEditor-Projects.dll!UnknownFunction
PackagingResults: Error: [Callstack] 0x00007fffc3d9801a UnrealEditor-Projects.dll!UnknownFunction
PackagingResults: Error: [Callstack] 0x00007ff60c632591 UnrealEditor-Cmd.exe!UnknownFunction
PackagingResults: Error: [Callstack] 0x00007ff60c63634f UnrealEditor-Cmd.exe!UnknownFunction
PackagingResults: Error: [Callstack] 0x00007ff60c62cfb6 UnrealEditor-Cmd.exe!UnknownFunction
PackagingResults: Error: [Callstack] 0x00007ff60c62d37a UnrealEditor-Cmd.exe!UnknownFunction
PackagingResults: Error: [Callstack] 0x00007ff60c630854 UnrealEditor-Cmd.exe!UnknownFunction
PackagingResults: Error: [Callstack] 0x00007ff60c646984 UnrealEditor-Cmd.exe!UnknownFunction
PackagingResults: Error: [Callstack] 0x00007ff60c648eb6 UnrealEditor-Cmd.exe!UnknownFunction
PackagingResults: Error: [Callstack] 0x00007fffe0617374 KERNEL32.DLL!UnknownFunction
PackagingResults: Error: end: stack for UAT