Trying to renew/buy annual Gold Live but says offer unavailable

My xbox is working i need help it say troubleshoot and everytime i restart it it say the same thing

You won't be able to add a stadard gold subscription while he still has Ultimate. You would either have to cancel the subscription or wait until his current subscription ends and then buy gold after Ultimate has completely ended.

brad, as much as I appreciate your help, it did not work, after I tried it I tried to start a party and it brought me to a page asking me to buy either game pass ultimate or gold, and I know this is not a problem with my gold, as I annually renew it and
it was very recently renewed.

If your oldest son doesn't need the account with annual subscription , you can turn off the Auto renewal.

Check the following support page to know how to stop Auto renewal#
support.xbox.com/.../cancel-xbox-live-gold-subscription

Regards

But I also paid an annual fee for Gold in December 2020 which was cancelled (upgraded) in Feb 2021 so I should have 10/12 of that fee owing to me. Can I redeem that?

When you son signed up for Ultimate, it automatically upgraded your Live Gold to Ultimate, hence why the next charge is March....so you won't have anything owed to you

After turning off Auto-renewal (as described by the IA above), wait for the GPU to expire (you've already paid till March anyway), then start Gold again. However, you can't buy an Annual live Gold direct from Microsoft anymore (far as I am aware anyway) so you'd need to buy a card from somewhere else if you want to buy a year at once