Hello ThyServant,
Welcome to Microsoft Q&A forum.
Halo have PC and Xbox version, which are independent from one another, so the PC version cannot be used on Xbox and vice versa.
Please note that this is a user-to-user support forum. Moderators, contributors including external Microsoft employees cannot directly intervene in Microsoft product features or access back-end systems. Our role is limited to providing technical guidance on reported issues, requests, or ideas. In this case, while I think the chance are slim (you redeemed through Microsoft Rewards and a long time has passed). You can try to contact Microsoft Support to see if they can help.
- Type Live chat in the search box.
- Now click Get help, and Select Contact Support or Sign in to contact support below.
- Go to the Products and services tab, and choose Other products
- On the Category tab, choose Billing and Account Profile questions
- Go to Confirm.
- You can now choose the option of Chat with a support agent on your web browser.
Thank you for your understanding.