Hi
@yellowmaticHave you checked if DEX is on? If so turn it off.
If that doesn't work press 3 line button in navigation bar (recent apps button) or open recent apps menu then scroll to the right and you should see virtual desktop (or more then 1) desktop 1, desktop 2 etc tap cross button and close it all with all apps running in that desktop, now try open app it should let open in full screen.