When you try to log in to a Creative Cloud application after updating the CC Desktop application, do you receive an "Unknown Server Error" message? This page offers solutions to fix this error. Try the solutions in order; stop when you're able to log in without receiving an error message.
Solution 1: Update to the latest version of the Creative Cloud Desktop app.
Solution 2: Clean up cached user login information.
Solution 3: Reinstall the Creative Cloud Desktop app and clean up cached user log in information.