Can't see a LAN / Can see a LAN, but can't join it.

If I share the game to a LAN, the other does not see it. If my friend share the game to a LAN, I can see it but I can't join to it. Connection error. Time Out... This came only recently. until it no longer worked.
But what this is ? Workflow !!! I dont understand anything. It worked before, even if the local hosted game is 0.0.0.0. All have the same version.