Full screen doesn’t work for me either. Either has the taskbar or a cubase grey color covering where the taskbar was. Either way I lose the bottom fraction of th screen. Only way it works is if I autohide the taskbar. But I hate doing that because I want the taskbar visible for general windows tasks. Not sure why Cusbase is so dodgy with full screen when practically every other program has a clean full screen.
Would be nice it Cubase had a full screen option like in Reaper. For example (F11) goes from maxim window with taskbar to complete full screen with no taskbar.