I saved a file I was working on to Adobe Creative Cloud two days ago and can't open it or an older version of it. When I try to download it I receive the message "Fehler beim Herunterladen" [Error downloading] (German PC), same with an older version. When I try "in Illustrator öffnen" [open in illustrator] Illustrator will start, but the file won't open and nothing else happens. If I already have another (local) file open in Illustrator, I will shortly see the message (screenshot 1)

Error Opening""

I may have had one or two unembedded linked files in the problematic file. When I save such a file I get the message in the second screenshot.

I have not moved the linked files on my computer in the meantime, and I haven't tried to open the file on another device either.