I have the same problem: I bought two games to play with my brother on the PC and already has a year I can not play coop with it! That is outrageous, the Actvision not aware of this problem and not do anything at all to resovler nor a satisfaction! this is a lack of respect for the consumer! If I knew the game would have this problem and it would not be resolved would not have wasted my time and my money i let alone buying something that, for me, not good for nothing because just bought because of the coop.
Demand a response from the company because I know I'm not the only one with this problem.