I get this error in VS:
Current solution contains incorrect configuration mappings. It may cause projects to not work correctly. Open the Configuration Manager to fix them.
I then open Configuration Manager, and click on Close and the error goes away.
I can then see it made these changes to my .sln file:
Why were the original configuration mappings incorrect?
It's not uncommon that shared projects get included in the list of projects to build. Not sure it applies to all cases but clearing everything between:
GlobalSection(ProjectConfigurationPlatforms) = postSolution
and
EndGlobalSection
in the .sln file and then reloading the solution will at least solve those.