I want to add an answer here as well. I have been building on disk D:. Just recently it stopped. The way I worked around it was to build and compile in Unreal. It works, provided there are no errors, every time. VS is a quirky beast. Try to use work arounds whenever possible. To add to this - my path was correct and nothing seemed different. I even went to a previous build but VS just would not complile and build.