I bought BO 2 because I wanted to play zombies with my friend, but the problem is, everytime I'm trying to join him (trough an invite or join session in progress) I get the error: Error, unable to join game session". When i send my friend an invite or he tries to join me in progress, he gets the same message. This is also for all my other friends on BO 2.
Does anyone know, what I do wrong or how to fix this? My NAT type is open
(This is on PS3!)