Looks like I'm not alone in this mess. Clicked to open illustrator 2021 this morning, and the indicator arrow shows below app icon but the program doesn't load. It is also highlighted in red in the force quit box. It started running diagnostics and recommended me do something with extensions, so I figured I'd just uninstall and reinstall. As I'm uninstalling, it just says "waiting" in the creative cloud box. Fortunately I have Time Machine working so I could grab the 2020 version I uninstalled a couple days ago.