01-06-2013 03:04 PM
Did you get the game used or new? chances are if you got it used, and it was already registered, you can't register it yourself. Think of it as a Windows Product key. Once someone claims it, its theirs. Giving a used one to someone else, that person will run into issues.
01-06-2013 03:05 PM
I had the same problem. The best thing to do is to contact Origin and let them know what is going on. If the Origin representative agrees that the code has already been used, they will give you a new code to try. If that isn't the problem, they might suggest to you what I had to do which is just input the code given through an expansion game.
More than likely though, if the code is saying it was already used, it probably was, and they'll supply you with a new one. Good luck!