Since the February update, some players have been unable to successfully update their version of Sea of Thieves from the Microsoft Store.
Workaround: Due to backend changes to the game, players will need to reinstall the game completely in order to play.
After uninstalling the game, if you are unable to access the download through the Microsoft Store, please try resetting your Microsoft Store and try again.
Though if the issue persists, you can also install Sea of Thieves through the Xbox App.