The editor fails to compile about 99% of the time. Open the project’s solution file (.sln) and press F5 to compile. If you don’t have a .sln file, you can right click on your project’s .uproject file and hit Generate Visual Studio project files. Also, make sure that the class you added has no errors. If I make a new C++ class, and it isn’t inside the root folder (“Source/ProjectName/”) I usually have to fix the include path for that class.
So for example if I create a new actor “MyTestActor” inside “Source/ProjectName/SomeFolder/” folder, then I have to change the .cpp of this class:
// From:
#include MyTestActor.h
// To:
#include SomeFolder/MyTestActor.h
I had a lot of issues with this when I was starting out, so hopefully this helps!