I think you should rather suspect an issue linked with the new feature to use the Creative Cloud desktop in PSE2021.
In my case, I aldready have a subscription. The first time the editor refused to open, the Creative Cloud also refused with an error. Rebooting enabled me to log in again. However I had to uninstal and reinstal PSE like @kandy_kan .
I would not be surprised if other PSE2021 users did uninstall the Creative Cloud desktop. There does not seem to be a difference between Win or Mac.