I have always left "Do not disturb" to on and disabled all app notifications in my windows 11 system settings. Today Dropbox posted a big popup in the center of the screen while I was doing something else. It was a notification that my free account was full and offered an option to upgrade or clear up space but no option to immediately close the window. It was also permanently on the foreground over top of other windows.
I can't find any options to disable this from happening. All notifications in the desktop app are already set to off. This type of behaviour is totally unacceptable. If I can't find a solution and it happens again I will have to uninstall.