I believe this is a bug repot.
I accidentally turned off one of my audio interfaces and I then turned it back on but not before Cubase had spawned a couple of dialog boxes. One was for the missing DSPs and associated plugins failure (Universal Audio plugins/interface). This went away but the second dialog could not be closed. It only had the directions without usually select list/radio buttons or OK button. It can’t be closed (see attached) without an “OK” button or X in the corner. I had to use command + Q to quit. The menus would drop down but items were grayed out, including quit.
That was followed by the usually OSX Problem Report for Cubase.