Problem with compilation Error:LNK2001

Development Programming & Scripting C++
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1

So I have been working on translating some blueprints into c++ and everything works fine untill I added 3 new classes, a BTService called BTService_SenseCheck, and 2 Actors called: AISound and AI_MemoryMarker.
I now get thees 3 errors after writing some code.

Severity Code Description Project File Line Suppression State
Error LNK2001 unresolved external symbol “public: virtual void __cdecl IGameplayTaskOwnerInterface::OnGameplayTaskActivated(class UGameplayTask &)” (?OnGameplayTaskActivated@IGameplayTaskOwnerInterface@@UEAAXAEAVUGameplayTask@@@Z) C:\Users\Desktop\\Intermediate\ProjectFiles.generated.cpp.obj 1

Severity Code Description Project File Line Suppression State
Error LNK2001 unresolved external symbol “public: virtual void __cdecl IGameplayTaskOwnerInterface::OnGameplayTaskActivated(class UGameplayTask &)” (?OnGameplayTaskActivated@IGameplayTaskOwnerInterface@@UEAAXAEAVUGameplayTask@@@Z) C:\Users\Desktop\\Intermediate\ProjectFiles\BTService_SenseCheck.cpp.obj 1

Severity Code Description Project File Line Suppression State
Error LNK2001 unresolved external symbol “public: virtual void __cdecl IGameplayTaskOwnerInterface::OnGameplayTaskDeactivated(class UGameplayTask &)” (?OnGameplayTaskDeactivated@IGameplayTaskOwnerInterface@@UEAAXAEAVUGameplayTask@@@Z) C:\Users\Desktop\\Intermediate\ProjectFiles.generated.cpp.obj 1

EDIT:
If I completly comment out BTService_SenseCheck.h and BTService_SenseCheck.cpp I dont get this error anymore, however if I just comment out the custom code I get this error.

2

Anyone has any idea? I can’t compile because of this and also not open my editor because I tried rebuilding project files.

3

forgot to add the GameplayTasks in build.cs

4

Thank you so much, . Your tip also worked for my project (version 4.17).