The error codes in Sea of Thieves are oddly named as if they were old pirate captains, but they have very valid explanations of how to deal with them. The AvocadoBeard error code is a relatively straightforward one that many gamers received when launching the game for the first time. It means the account you are trying to play in Sea of Thieves does not have access to Xbox Live and you cannot log in to the game because you cannot play it offline. It means the same if you're trying to log into the game on Steam, which is confusing because you don't need Xbox Live to play the game through Steam.
If you're playing from an Xbox One or through the Xbox beta app on your PC, you must have Xbox Live on your account if you don't have an Xbox PC Game Pass membership. Make sure the credit card or payment information you are using is valid and has not expired. After resolving the payment issues, you should be able to reconnect to the game without any additional issues. The same goes for those who have an Xbox Game Pass or PC Game Pass subscription.
For those who experience this issue while playing through Steam, check again the Microsoft account you're signing into Sea of Thieves. If you log into the game that is not logged into the Steam account that has Sea of Thieves, you will see the AvocadoBeard error message. To make sure you're using the correct Microsoft account, try signing in to Sea of Thieves by clicking directly on the app through your Steam library. If that doesn't work, visit the Sea of Thieves website to recheck the Microsoft account you have there is linked to your Steam account, which could be causing the issues.
To verify that you have the correct account, you can uninstall it from Steam and give it a clean install. This way, you will be able to sync the correct accounts together, mainly if another Microsoft account owner is using the same computer.
