I bought Bo6 but it’s saying I have to buy the game again despite already having it and had...

Hi Alexandre, my name is Rodrigo. I'm an Independent Advisor and a member of the Microsoft community and I'd love to assist you today.

I am sorry to hear that.

Please, reset the store and try installing the game again.

To Reset the Store, Press the Windows Key + R > Type WSReset.exe and press Enter.

Close the store and reopen it.

Then, on the Microsoft Store, type your game name: "Sea of Thieves".

Load the game page and click on "Install".

Let me know if it works!

just to clarify it is the same account and I cant find it in the purchase history

In a case like that it is likely an issue of not being logged into the right account. Double check that you are logging into the correct Windows 10 account and not a guest account by accident, I can almost promise that is the issue you are running into.

I don't have an email receipt but the transaction shows up on my bank app

Make sure you are logged in on Windows 10 with the same account that was used to purchase the game, then check again. It should show in your library on the Microsoft Store.