Code was already redeemed

Please contact Xbox support from the account you tried to redeem the code, provide them the key and ask for the exact time and date of when the key was activated. Specify that you don't need to know who activated, just the time and date of the activation.

Here are quick instructions on how to contact Xbox support:

1. Visit the Xbox Support page and click the Contact Us button.
2. Select the Subscriptions & Billing category, and then the I can't redeem a code sub-category in the popup window.
3. Select Chat online.
4. Input a short summary of your question.
5. Wait to be connected with a support agent.
6. Upload screenshots of their response. Make sure that the code is visible in the chat window.

Make sure this information is visible in the screenshot: