When I try redeem my code it says it isn't activated

Have you tried going back to the store that you bought it from and asking them to activate it properly ? If they can't/won't then try contacting iTunes Support (you will probably need to give them images of the front and back of the card, and possibly its receipt) : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then iTunes Cards And Codes