"Your Code Has Already Been Used"

[ExKage]

I did the same but upon getting to the https://preorder.na.finalfantasyxiv.com/ page, it tells me that my code has already been used. So at this point I'm worried perhaps something is wrong, but I'm going to wait until the purchases calm down and retry.

I know someone on /r/ffxiv reported the same thing. I recommend calling support.