Asking me my Registration Code again

I can't log in again after i logged out it's asking me my serial code a second time for no reason, it's the same on the website. When i enter my code from my account it says its already registered

I resolved my problem alone it migth help you too, i received another email of confirmation from S-Enix at the bottom they where another code under :: Digital Rights ::: i entered that code and it works again

Preorder/Early access code is different from the actual game code.
If you're trying to use that code again it will fail.

You should have gotten another mail or the boxed product which has the game code that you need to register.