Answered by Mukesh
Start by entering the code carefully, since many codes mix letters and numbers that are easy to misread, and a single wrong character will stop it working. Copying and pasting the code where possible removes that risk entirely.
Next, make sure you are redeeming it with the correct brand and in the right place, because a code only works where it belongs. If the brand's site reports the card as already used, retrace whether it may have been redeemed before, perhaps by the person you gave it to.
If you have checked all of that and it still will not work, contact our team with your order reference and the details of the problem. We can look at the order from our side and work with the brand where needed, so a genuine issue gets put right rather than left with you.