"Unable to connect. Please restart your client.F2P/SIG: no_session(Empty Auth from Discovery)"

Hello, 

My son keeps getting this error when trying to join a friend:

"Unable to connect. Please restart your client.

F2P/SIG: no_session(Empty Auth from Discovery)"

We have all the updates and we have tried to restart our Xbox, but it's not helping. Attached a screenshot of the error and our Minecraft version (cause I'm not sure I chose the right one from the provided list).

Username: Karden241