I've had some difficulty with ASC today too: launched an update for Piano V, which seemed stuck mid-download. I couldn't launch anything else, say installing Analog Lab V… except I had managed to uninstall Analog Lab 4 just before (with the update to Piano V already running, if not that well).
I tried the "usual" bug fixing method: turning it off and on again. Had to kill ASC from task manager, then another ASC process that remained in the backgroung. I rebooted my computer and, when I relaunched ASC, it updated itself, forgot it was trying to do stuff to Piano V, and worked like a charm for the few things I had to update or install (Pigments, Analog Lab V, Piano V).
Hope it's as easy for you!