Hi, thanks for replying.
I confirm that in the connectivity menu there's nothing to select: everything is gray apart from "closed", and if I select it I cannot modify it.
I checked many times the options, but I fear that the PS4 menu is different from pc because there are not any settings for multiplayer connections.
Today I will try to export my savegame to the other PS4 and verify if the other one can host the saved game.