There are a few reasons this might be the case. 1. The code you recieved can only be used once by the person who originally placed the order. Ie. You can't give the code to a friend and have them redeeem it. It won't work. 2. If you are the person who bought something before, you need to add at least 1 other item to your cart for the code to work. Make sure you've got another item in your cart or the code won't work.