Limited Edition Map Pack Code Not Working

Hello, I just opened my New Limited Edition Copy of Halo 4 and when I enter the map pack code in it says the code has already been redeemed and it doesn’t work. I purchased it new, from Gamestop and don’t know what to do. I just want a map pack code that works. Please help. Thanks

Talk to Gamestop. Looks like the product wasn’t as mint as they told you.

You 100% sure it was new? Try to discuss about it where you bought it.