Hi - I'm happy to help with your Mac issue. Please remember to Accept when we are completely finished and you are satisfied with my answer. Are you certain that it has not already been used? Also, was the code compromised when you received the card, meaning was the code visible when you received it? There are bad people in the world that compromise codes at the point of sale and you unknowingly buy a card that has been compromised. To be sure, you can contact iTunes support at this link http://www.apple.com/support/itunes/ and talk to an Apple rep about your problem. There is likely noting wrong at your end and it will need to be solved with support.