This is an ongoing problem which crops up with new threads by new people it hits every month. Far as I am aware they still don't really know how to fix it. My boyfriend has about a month left on a 2 month gametime card he was forced to buy in order to continue playing...will have to see if it has been resolved for him at the end of that time or not.
So far suggested fixes from CS have included making sure the address on your eso account EXACTLY matches that on your cc (no abbreviations, no extra initials, no commas or anything else in the the wrong place) and changing your email address.
I just got the same issue.
"We were unable to process the payment for your subscription to The Elder Scrolls Online. Without an active subscription, you won't be able to continue your adventure!"
But PayPal and my Bank show the withdrawal and payment as complete. Why is there a discrepancy?
EDIT: Just received this
"Thank you for coming to The Elder Scrolls Online Customer Support Team! I'm sorry there is some confusion with the two reports. I'd be happy to look into this so you would no longer need to be concerned. I took a look at the account attached to xxxxxxxxxxxxxx and I see you in your billing history that everything is going swell. We are in the final stages of payment and you should be able to access the game. As to the reason for the e-mail that is indeed interesting.
None of your past transactions had any issues with our system and so there is no reason you should have received it that I can discern from your records. I would say that you can disregard it, but of course keep it in hand for the sake of future reference if you run into any other troubles. In the mean time you should have find in your renewed game time!
Finally, I apologize for this false alarm and the inconvenience it has caused you."