From a tweet that Marcus received from a guy that was having problems with it asking for the reddem code over and over even though he already put it in:
"First, I simply redeemed my code from the booklet. Next, I kept clicking xbox live on the main menu then thats where that "attention" screen kept popping up with the 3 options (redeem, purchase, start trial) over abd over again. Finally, I simply exited to the dashboard, restarted my game then a message popped up saying I have Online Axxess. And boom! Everything is fine and dandy."
So, after you put in the online axxess code, you may need to restart that game for it to register.
...just so no one here (including me) freaks out, lol.