Me and my friend are trying to play a zombies custom game but when he sends me an invitation or I send him one the game looks like it has "refreshed" or something, they I try to join him again through the friend list or by invitation and the game shows the Treyarch loading logo and then shows a the message "unable to join game session".
We tried inviting when we are on the lobby, also we tried joining when the game starts, even we tried with the old methods like joining by IP address or using the console command "zombies_minplayers" but nothing works. When we try to join through IP address it shows a message that says "joining game session" but nothing happens.
We both have Upnp enable, the right port fowarding, even we allowed the plutonium through the windows firewall.
And we think this is strange because we played without a problem 2 months ago using the bo2 friend list, I hope you can help me :(.