PackagingResults: Error: Unknown Cook Failure

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UATHelper: Packaging (Windows (32-bit)): LogInit: Display: LogOutputDevice: Error: Ensure condition failed: ShouldSerializeWidgetTree(TargetPlatform) == false [File:D:\Build++UE4+Release-4.18+Compile\Sync\Engine\Source\Runtime\UMG\Private\UserWidget.cpp] [Line: 1721]


I had the same error for a 3 months and finally got it to work! I’m not 100% sure what it was in the end but i think it was to do with the content of the project. Make sure that all document within your “Content” Folder (PC/Documents/Unreal Projects/“Project”/Content) are the same as all the assets in your unreal project.

When deleting items within the UE4 project for some reason they don’t delete in the Content folder or vise versa. Causing a problem when cooking as it is not able to find the right documents.