Smn842's post in Missing floor and ceiling materials was marked as the answer
You've got "Rooms" turned off in Tools -> Display Options -> Layer Display Options.
Smn842's post in Tiled Windows was marked as the answer
I don't have any such issues with that view layout.
In fact I often have several main windows for HDP open on separate monitors some with two or more views each and no blanking on any as I switch between them.