redeem code for 12 Month support not working

If you have a renewing 12 months subscription and wish to redeem 12 months PPC, they can just cancel the current 12 months and waive off the renewal charge for you to redeem the code. Please contact Xbox Customer Support to process it for you.

You can keep trying to work with support, but without the code there really isn't much else that can be done. It sounds as if the code didn't redeem properly. Trials (the 14 day code) do not stack so the 12 month code should have overwritten that code
if you redeemed them at the same time.

I watched the video and tried to redeem the gift card that way and it will work but what I would like to do considering Xbox Live for 12 months is on sale right now is use this gift card for that but when I go to the Microsoft store and I click on deals
and redeem a code for the 12-month membership at the discounted price at tells me that their code is not found, although it does work the other way which is the 6-month option but I'm aiming for the 12-month

Have you redeemed the 12 month code?

It's frustrating, I and my brother had the same issue. I got him a 12 months code as a present for Gamepass Ultimate. The plan was to first pay only 1 GBP for the first 3 months and then redeem the 12 months code on top of the 3 months. But it didn't work.
We tried from both Xbox and Browser