I bought game pass ultimate but its still showing only the buy button fotr sea of thives...

Hi Rajo!

Please confirm on your account services page on https://account.microsoft.com/services if you have an active Game Pass for Console or PC.

Verify that you're checking the right account by checking your profile on https://account.xbox.com/Profile if it shows your correct gamertag.

Then:
Launch the Xbox app and sign in with the Microsoft account you use for Xbox.
Select your gamerpic, then select Settings.
Under Account, select Change my Microsoft Store account.
Follow the on-screen instructions and sign in to the Store with the Microsoft account that has the subscription.

I believe there is a problem of the game itself to me and it happened with sea of ​​thives, a couple of months have passed to unlock them

The update of sea of thives!

I play Halo 5 and Sea of Thives

Hi there! This is Virginia O.

I understand that you want to know more about buying the game Sea of Thieves.

I apologize for the inconvenienced this has caused you. I will do my best to help you.

Yes, if you buy Sea of Thieves without a Game Pass subscription.

You only need a subscription like Game Pass Core and Ultimate pass for online multiplayer access, which Sea of Thieves requires because it’s an online-only game.

Thank you for your cooperation.