[PS3] Coop Splinter cell: Blacklist

Hello, well my problem is, I tried to play with a friend but we could not, we made the attempt on the day of the launch.
play in an open session is to have with other players but not with this friend in a private session whether the invite me or I him.
Also the to have played in an open session.

Help please, as we both want to play this wonderful game :D