How are you creating these files? Are you adding them through VS or are you using the “Add new C++ class” wizard within UE?
I don’t have a direct answer but what I can say is that I’ve had issues in the past attempting to simply add files through VS. I seem to be missing a step that the editor wizard takes care of. That is not to say that it’s not possible to do it all straight from VS but it requires an extra step that isn’t clear to me at this stage. Since then I’ve always just used the wizard rather than fighting it.
EDIT: To be clear, the extra step seemed to be more than just regen’ing the project files. It seemed like maybe I was violating some pre-ordaned/expected file structure/pattern on top of that.