Following 1.13 update unable to join lan games when signed in using MS Child Profile

My son is unable to join LAN multiplayer games (or see any server hosted games) following the 1.13 update. Prior to this we have all been able to play together.

 

Env is 3x Windows 10 laptops all on same Minecraft version.

When using my adult profile, I can see LAN games and server games.

One of my sons not using MS logon can see and join LAN games on 1.13.

Other son signs in using MS Account (child account) and cannot see/join any of the LAN games.