Cant connect to friends(brothers) lobby???

I used to play this game a lot and this is the first instant iv come accross where i can not connect to someones elses lobby. Usually if it does happen, its a temporary problem but the game just does not want me and my brother to play horizon together fullstop. If i create a game and i invite him he cant join, same the other way around. We can see all the same lobbies but can not join together. If one enters a random lobby, we tell each other the name of the host, the other tries to join but it wont work. We then switch roles, 1 goes in first the other one tries to join after but it wont let us in to the same lobby.

Can anyone help?
Is there something that can be done either end to help fix the problem?
His IP is TalkTalk and mine is Sky, Make a difference?

WOW!! The Horizon community really has fallen…

Anyway, The problem seems to have fixed itself. Random!

i thought it would of been your nat type you might need too set it to open on your router