I have been experiencing the same error myself since Aug 18 2013.Repeated calls to support since then and all the suggested ideas they provided didn't work. Here's my understanding of the subject at hand so far...
Stage One: Registration : Error code 601:
If you're receiving error code 601 then this means that your SE account blocked the card you're using. Suggested action is that you should unregister the card and wait complete 24 hours before trying to register it again. Unfortunate though, some cards get permanent block. Hence if after 24 hour pass you tried to register the card and STILL getting the same error code 601, then I believe you have 2 choices:
A) Call them and pray to God they release the block on your card. (good luck!)
B) Use another card. But don't forget to change the billing information name if you're using someone else's card because the name in the billing info should match to whatever card you're using(or so I think.) You can change it by going to
http://eu.square-enix.com/en/home login and then go to user settings > extended information and change the name to the name of the card that you're going to register in the account management site.
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Stage 2: activation: Error code 401
If you are able to register the card but unable to reactivate because of this error, I am sorry to tell you that you're options now have become much more limited. Hence I can only suggest the following:
A) Request to unlink your Play online ID from that SE user. Don't tell them that it's because of the card because they will not accept that and hence won't allow you to unlink it. Tell them that you need to unlink it because your pc was hacked and your account information is not safe. The process of unlinking the account could take weeks knowing SE bad customer service reputation and actions..However, I know someone that did that and then the card was accepted on the new SE user account. Which basically implies that this error is only generated because of the SE user account that might have gotten certain restrictions that won't allow you to make any payment.(This is still is only a theory so I can't guarantee you that it will work after you relink to a new SE user account. Do it if you have no other choice..)
B) Forget about your old content IDs, make new SE account, buy the whole freaking game and add-on codes again and link them to that new SE user and try to pay. (only if you have much money on your hand that you don't care to waste, and ONLY
at your own risk. Don't blame me if this still didn't work for you.)
C) Quit the game and wait until you hear of another lol-payment-method introduced for your region.
D) Keep calling them and waste your time and money on international calls. From my experience I can frankly tell you that they will never remove that restriction on your account. They know how to calm you down, but don't know how to do their job. Their direct line is 00448706000182 so good luck. If you rather try the chat service instead, you will be lucky if an agent replies to you who actually KNOW what this error is. Oh and last if you try their email support, they'll simply reply after 48 hours that your case had been closed and that their priority is to solve FFXIV customer problems. Good luck anyway with all 3 options.
E) You can still try another card.... Always remember to change the name like I suggested above if you're going to use another card with different name than the one registered in that website.
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This indeed is frustrating and I can really feel the pain you're going through just to play again, but with SE service support, STILL you should never loose your temper on the person you're speaking to as this might also lower your chance of solving the problem at all. Keep calm and take all the bull you're going to hear from them and do what they will continue to suggest if you decide to stick to calling them.
@Banota: as for your $200 offer, I can only tell you that its really not worth it. Why would you pay this much to anyone just because SE can't fix their own errors? I know you want to play.. But trust me there are more better games out there that you can still have fun with until you find a way to figure out how to solve these technical errors. I promise to keep you posted if they update me with anything that works here in this thread.