https://www.gamespot.com/articles/sea-of-thieves-not-accessible-through-xbox-game-pa/1100-6457722/

Microsoft's Netflix-style subscription service, Xbox Game Pass, has been available for some time now, but it took on new value when the company announced plans to launch its first-party exclusives on day one through the service. That started with last week's release of Sea of Thieves, but due to a new problem that has popped up, the game isn't currently playable for Game Pass members.