I had the same problem. When I installed GP premium my doamains were subfolders like anis.af/quizzes/ and then I changed them to subdomains like quizzes.anis.af and update failed.
I came here to my GP account and deleted all subfolders then added all subdomains and update was sucessful!
having an active key did not solve my problem until coming here and fixing the problem in my account.
I was trying delete and re-install GP-premium plugin but still failed update and there was comment as “Update Failed: Could not create directory. gp-premium/library/customizer/controls”. do I have to make directory?