I have now an Idea why.
After browsing through the SpyfullModuleRulesSourceFiles.txt i see this:
“C:\Game Development\Projects\Spyfull\Plugins\AdvancedSessions\Source\AdvancedSessions\AdvancedSessions.Build.cs”
so… the Problem is there is no AdvancedSessions.Build.Cs included in your newest Update.
edit: Fixed it myself now, just putted in the old Files from the .zip before (I still had them)