Hello @sebeag, thank you for reaching out.
Have you tried to restore a save backup from the cloud saves?
We’d suggest that you first ensure that your save is stored on the XBOX cloud, before trying the following steps:
Reset the console cache by holding the power button for about 10 seconds until the console powers off, then disconnecting it from the power outlet for a couple of minutes, then try loading into your SP session.
If the issue persists, try to perform a soft factory reset while keeping games and apps.
Should you still have trouble loading into the SP game, please try to do a full reinstall of the game.