To anyone who order online and received a key that was already taken or invalid call Gamestop and they will send you new ones. I got my two keys on the 21st and my friends that I gave them to, tried activating them this weekend, only one worked. So I called up Gamestop and they gave me 2 new ones. It took them less than hour to email them to me.
For those of you purchasing IN-STORE, they are currently having an issue with the key generator system, and there "IT Department" is currently fixing it.