I have just been able to pay my bill! I emailed them AGAIN and got a response back. I clicked on the link for the ticket and it took me to a new portal! Client Area - Gamers Services I then logged in using my normal details and bingo I could pay!
I have a $5 a month and was on mint/gmasterpanel
In the email it also gave me a new filelinked in number, which I just logged into.
The GMX app is gone and obviously not working but there are guides to using and downloading other apps to run the service.
ENJOY!
Thanks for posting -- I was able to log in and pay, too. (Had a Mintpanel account, though not one of the grandfathered ones.)
I'd already signed up with Sapphire as a backup, and for five bucks a month, I think I'll hang on to it. Cheap insurance! lol