I was with the same problem today and I got a solution:
Project Recovery in Unreal:
Delete files on your project:
Binaries, Intermediate, .vs, Saved, DerivedDataCache, .sln (not always necessary)
In the .uproject file → Generate Visual Studio Project Files;
Open the .sln and compile the project;
If you still have problems, recompile the project solution.
All steps must be followed with Unreal Engine closed.
furthermore, I had to fix my code by doing a forward class declaration on my header class, because I have a pointer of another class as an attribute of mine.
Sorry if there is any english mistake.