I can't upgrade xbox live gold to xbox game pass ultimate.

Hi,

Once you upgraded to Xbox game pass ultimate, your Xbox live gold will be carried over to Xbox game pass ultimate. For example, if you have Xbox live gold for a year and you upgraded it to Xbox game pass ultimate, your Xbox live gold and xbox game pass for
console and PC will also be good for 13 months (12 months Xbox live gold+1 month upgrade Xbox game pass Ultimate). If you cancelled the Xbox game pass ultimate, automatically your Xbox live will also be cancelled since it is already merged to the Ultimate.
You need to contact Xbox Support to reinstate your lost membership.

To contact them, please go to this site:

https://support.xbox.com/en-US/contact-us

What happens to my prepaid months of Xbox Live Gold and/or Xbox Game Pass when I sign up for Xbox Game Pass Ultimate?

When you subscribe to Xbox Game Pass Ultimate, we’ll apply any prepaid time you have on Xbox Live Gold and/or Xbox Game Pass toward the Xbox Game Pass Ultimate plan, up to a maximum of 36 months. Prepaid time conversion rates are subject to change.

TXbox Ultimate Game Pass 1-month sub is $1 on XBL, includes Game Pass for PC, Xbox One, and Xbox Live Gold. Purchasing the $1 plan will upgrade your existing Xbox Live Gold/Game Pass memberships to Ultimate and combines both subscription months as Ultimate

I can't put my finger on the conversion rate data, at the moment, but it's approximately 3:1 Gold to Xbox Ultimate, if I recall correctly.

You can add the Xbox Live Gold and Game Pass code then upgrade to Ultimate. The Ultimate will automatically be extended by the amount of months of the Xbox Live Gold plus the amount of months of the Game Pass code.

If You Get Game Pass Ultimate It Will Convert Your Xbox Live Gold 1 Year Into Game Pass Ultimate For The Remaining Time Left On Your Year Subscription. So For Example If You Have Xbox Live Gold Paid For A Year And You Upgrade To Game Pass Ultimate It Will Convert It To One Year Game Pass Ultimate Or However Many Months You Have Left Of Your Subscription.

(Make Sure It Says Upgrade To Game Pass Ultimate So It Will Convert Your Gold To Game Pass)

As Smwutches said, Game Pass Ultimate is Xbox Live Gold and gamepass combined it wouldn't make sense to have Xbox Live Gold and Game Pass Ultimate so it upgrades.

As far as I know, the £1 deal is to upgrade only anyway Not to buy out without Gold. You will have to buy Gold again unfortunately.