Had a friend with the same issue. Tried many different types of cards, even tried paying for his account myself, nothing worked.

Eventually we decided to go ahead and try using an Ultimate Game Card. We went to pcgamesupply.com, bought a $20 game card, went to the mog station and added Crysta (2000), then payed for time for the game with the crysta.

It has worked and he's been able to play ever since. The only downside is it cost more this way than paying the usual $15 a month.

So, bullet point for you guys.
  • pcgamesupply.com
  • Buy an Ultimate Game Card (at least $20 so you can get at least 2000 crysta)
  • Add crysta to your account through mog station or account management (takes you to the same page)
  • Go to mog station and pay for your subscription using crysta

Hopefully this works for more than just me.