I've got the same problem as well. Played during the early access but now I can't log in anymore, due to my code already being used.

On the mogstation it says that I don't have Heavensward, but when I check Square Enix's website it says that I do have it registered...

I mean, my character is an Au Ra, I have an astrologian and a dark knight, a lv 50 machinist and a lv 51 white mage; so to me it's pretty obvious that I do have the expansion installed and registered.

I bought my (downloadable) copy of Heavensward from Square Enix's online store.