Check these
- Your own balance or library on that service. If the value is already there, you redeemed it and forgot.
- Any other account of yours on the same service, including one on a different device.
- Whether you shared the code, posted it, or sent a screenshot of it anywhere.
What to do
If it was not you, this is a real delivery failure. Use Report a problem, choose not working, and attach the "already redeemed" screen exactly as it appears.
Do not delete anything and do not order a replacement yourself. The claim is judged on that screenshot and the delivery record on the order.
Never post a code publicly, even partly blurred. Anyone who can read it can use it, and a code redeemed by a stranger is not recoverable.