Does anyone know why I cannot play the game anymore?
I've found in my old hard drive the files of the game and the PreLoader executable, but when I try to open the game itself just nothin happens.
I'm not interested on playing online, just want to play the base game offline.
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 :(.
I just have one more question, to play with my friends I have to do it in LAN mode or in Online mode?
Yeah I've tried with that but I just tried with the public IP or something like that so I will try with the priv IP, thank you.
I can't do it, it says that requires an external IP address and if I put the ports 4976 to 4977 says it's wrong.
I just have that option and another one called "Port Mapping" but it doesn't let me put TCP or UDP protocol. That section looks like this.
Yes, we start the match and then we tried to connect. The first image is from my router. 
The second one is from windows firewall.
I guess it's failing because I put the ports in a wrong way.
I've already tried with the most common ways to do it but always shows a text that says "Joining game" and nothing happen.
I've tried joining my friend by the friend list, using the command to connect with the ip address and port of plutonium, even using an app like radminvpn but nothing works. Also me and my friend enabled the ports on the router config and the thing on windows firewall.