I am unable to redeem my limited edition code from a physical disc copy of Crysis 2 purchased from a retail store.

Your purchase transaction was received.

The status of your transaction is shown below:
Promotion code was not found

Does this means the code is invalid, have not been activated yet, or redeemed by someone else already?

Maybe you have to wait another 7 hours.
EA has been doing a lot of crazy things lately.