Well, I don't know if it'll work on your case, but try to register it as a service on you account in the Mog Station system. I got my code today and got the invalid code error in the FFXIV registration page too, but it worked on the Mog Station.

External link here: https://secure.square-enix.com/accou...est=mogstation

Update: Also, don't flood. This isn't cool.