Can no longer join friends' words (even when sharing LAN), can no longer join realms.

Can no longer join friends' words (even when sharing LAN), can no longer join realms.   My son and i have made no changes to our minecraft or microsoft settings.  All account settings appear to permit multiplayer.   We used to play together all the time, sudeenly stopped being able to join each other's worlds.   Problem started approximately 1-2 weeks ago.