Xbox Game Pass received from Nitro Discord didn't work

I tried using the code received from my Nitro subscription to extend the period of my subscription of game pass ultimate.

The appeared to be working, and even informed me that the 3 months of xbox game pass would be converted to only 2 months of xbox game pass ultimate.

Still, the code didn't work and if i try using it, it says the same has already been reedemed.

How should i procced?

Thank you in advance and brgrds.

:)