I saw this posted already but with no answers. For some reason, I can no longer edit the faces of geometric items within my levels. When I click on the face it never becomes selected to let me drag it. It had worked fine for days and then stopped.
Make sure you are in the right Mode, in the Modes panel
Confirming that I am in Geometry editing mode and have recorded what is happening. (Note I was left-clicking the entire video)