I'm having the same issue. I keep getting the error "Unable to Sync due to server error". I checked my storage and I have only used 10GB out of 20GB. All of my files used to sync just fine. It started with jpg files not being able to sync but now it's all Illustrator and pdf files. I tried uploading online but I got the same error as Andrea. I even took a file that successfully sync'd up in January and saved it to a folder titled "February" and that file will not sync up. Help!
My archive had a few files in there but it is now completely empty.
The error I am getting is "due to server error".
I turned off the sync and restarted my computer. After it rebooted I turned sync back on and I am still getting the error.
The 10GB of 20GB was from my settings online as well as the Creative Cloud app under Assets/Files. After emptying my archive I have used 9.5GB out of 20GB, less than half.
It first started back in late January when I noticed a Illustrator file that I exported as a jpg would not sync. Then it was a couple of pdfs but now nothing will sync. I've taken AI and PDF files in a folder marked January that still show a green check as syncing up, created a new folder called "March" (the empty March folder will sync) and then copied those same files into the new March folder. Those files will not sync up. The newly created folder will sync but the files will not.
I got feedback from our engineering, so hopefully this should help. Your issue is similar to Andrea's.
This is the issue, it appears you're trying to add more files to a shared folder and the OWNER of the shared folder has exceeded his/her quota, this in turn causing you to see the failures on your system. I'm sorry the errors weren't more clear regarding the cause.
If you attempt to add/sync files which are not part of the collaboration it should be able to sync them successfully. The icon for folders which are part of a collaboration should appear different than those which aren't.
Let me know if this helps and if you have questions.