https://wccftech.com/sea-of-thieves-patch-hotfix-loading/

Rare is currently rolling out a new Sea of Thieves patch that fixes the infinite black screen issue on both Xbox One and Windows 10 PC.

Following the deployment of Sea of Thieves update 1.0.8, many players reported being caught in an never-ending grey/black loading screen. So far, the only solution was to kill the game and reload. It appears that developer Rare has now found the cause of this issue, and a hotfix is being deployed. The hotfix weighs in at approximately 120/150 MB respectively for PC/Xbox.