Failed to load file *.generated.h

I am puzzled with an issue I have right now.
I had cpp class generated via UE4 some time ago which had no problems for a couple of months, but today when I wanted to use this class I couldn’t - build tools complain that Worker.generated.h cannot be found/open.

The thing is - file is there AND visual studio shows it in the External Dependencies (see screenshot)

What I did so far:

 1. Removed .vs, Binaries, Intermediate, Saved folders as well as *.sln file.
 2. Re-generated project.
 3. Used VS 2017 and 2019 - no difference, they both see that file but fail to compile.
 4. Explicitly add a folder into include directories list.

I know that most of the similar errors reported are related to IntelliSense been not working, but it works for me here.
Also, I have multiple other classes which include *.generated.h and they work just fine.