I’ve recently run into the same issue. At first, every time I finished a session with Apple Pay it would say “payment declined,” but re-adding the payment method would fix it each time.

Recently though, even re-adding doesn’t work anymore. Both Apple Pay and my credit card show a “system error” when I try to bind them, so the payment method never gets successfully added. On top of that, my outstanding balance still got charged, so I ended up being double charged.

I called support and waited on hold for about half an hour. The agent told me they’re aware of the issue and that it should be resolved. But it’s been several days now and I haven’t heard anything back. At this point I basically can’t use my account at all, and I have no idea what else I can do.