Can't join a listen server create for a LAN Game

[Double Trouble]

Hi
Since a couple of month (an update of source i suppose) , i can't join a listen server create for a LAN Game. THere is no server listed in LAN Games and no friends are playing in the local area.
If somebody i doing a Maj-Tab do join my server , he get the answer " X is not running a server" despite the server is running and can be join from the console by the ip.
I have 4 PC, same Group and it was working in march-may 2017 but since this summer = niet

I can join the game by "connect 192.168.0.MyIP" and it works but the server never appears when looking for server...
It's the same things for TF2 (its works from the console but not in "find server"

any idea ?

(Sorry for my English..)