Returning player, help

[Yuyun]

You have bought the complete edition which includes ARR + Heavensward + Stormblood. Right?

Your also have registered ARR + Heavensward on your account before - while you were playing on PS3 - which is now converted to a PS4 access for ARR + Heavensward. And you can log into mogstation for this account fine, right?

So, you should have only bought Stormblood for PS4 because you already have the other two registered on your account for PS4. You can only have one copy of ARR registered for each platform. And that's why it keeps telling you that you need to create a new account for your new purchased copy.