Good luck my friend. I have been in a back and forth since yesterday with support. Someone will reply to this thread to tell you that someone will be looking at your ticket soon. But I can save you the trouble. They will ask you to provide proof of purchase. Then when you provide proof of purchase (possibly more than once like I had to) they will possibly give you a copy paste reply that has nothing to do with your problem. Then when you call them out on it they will tell you that the seller should have given you two codes and they are sorry they cannot help you. Then when you point out that you gifted a prepurchase of the very same digital upgrade to a friend (from GMG no less) and they only received one code that unlocked everything so the problem must be on their end they will just regurgitate that you need to contact the seller.
As I stated before. Good luck my friend.