This all started when I couldn't run Illustrator anymore, it would just be stuck endlessly on the opening page, with different login backgrounds visible each time. So I decided to delete and wipe everything with the Adobe cleaner tool.
After cleaning everything and removing OOBE and SLCache/SLStore etc, I tried installing again, but this time got stuck on an endless login where Safari would open a page to login, say 'you're all set', then take me back to the installer, which would spin the wheel a bit then go back to the login page, endlessly. If I interrupted the process and clicked on manual login in the installer app, it would say "Server Disconnection Error".
Upon troubleshooting this I found the Adobe help page,
This had a useful set of steps to troubleshoot problems connecting to the activation server. I could activate manually and all that, but if I then "Start a web browser and open one of the following links, depending on the version of your product", I would not get the successful "pong" message on Safari, but rather this:
If, however, I switched to opening that link in Google Chrome, I got the successful 'pong' message.
So then I tried to switch the default browser of my Mac to Chrome, hoping that the Adobe CC installer would then use that to try activating but, sadly, it persisted in trying to authenticate using Safari under the hood even though the OS's default was set to Chrome.
In effect, I cannot run or install any Adobe CC products I paid for until either Apple fixes some underlying Safari problem that was likely recently introduced, or Adobe changes its software to use an alternative authentication method.
If anyone has encountered this issue and managed to resolve it I would be very grateful!
Update - now even Safari gets the successful 'pong' message using the authentication server connection test link on the Adobe support page, yet the same endless login loop is presented. If I interrupt it and try to sign in manually (by clicking on "If your browser is not responding, sign in here") I get this:
Of course, there is no such problem as I can connect to the authentication servers fine via the test link as well as following all the steps in the help page for this 206 Error code, including changing networks, repairing the hosts file, etc.
It looks like there is some deep problem in the software. Not sure what else to do at this point short of asking for a refund of my recently purchased annual CC subscription.