I've had this error for about 3 days now, currently trying to fix it. However, I've now noticed that it's going to be almost impossible without a game card of some sort. Unfortunately I live in Argentina, and am unable to purchase any sort of game card at local stores. I've already contacted Square Enix three times in two days, the support being completely useless. They simply state the same situation like brainless monkeys. "Oh, I'm very sorry about that. Mhm? Oh yes? Well you should try and use Ultimate Pay. Oh you can't use Ultimate Pay? Wait 24 hours, then try your card again. We're very sorry, you can buy a game card!"
After I've told them multiple times there's absolutely no means for me to purchase game time without using Square Enix, they continue to give the same advice.

What had happened was I had to change my debit card, and what a mistake that was. Now I've had this 401 error and it's been well over 48 hours. I'm going to see if I can get a family member living in the US who can buy me the card, if that doesn't work... well thank you Square Enix for robbing me once again! (Was hacked by RMT sellers on the 2nd day of play, didn't get m account back until 2 1/2 weeks.)