Hi,

It looks like there's an issue with a file that was previously cooked. One possible and easy fix is to delete all cooked and intermediate files from the project. These files are located in the Unreal Project's root folder under the \Intermediate and \DerivedDataCache folders.

If that doesn't fix the problem, you likely have an incorrect "ProjectName.Target.cs" file. These files define how your project should be built and what target platform it is intended for. We could better understand what's going wrong if you open this file with a text editor and copy its contents here.

Warmest regards,