Receiving Error when trying to join friends/friends join me.

[TheLivingRcJ3]

Everytime i try to join my friend on the Black Ops 2 Zombies mode it takes awhile to load then sends us to the main menu saying "ERROR, Unable to join game session." Does anyone know a fix to this problem?

[Resxt]

https://plutonium.pw/docs/custom-games/#t6

[gstarr]

Resxt that doesnt work i added my friend and when he or i go to join eachother it just loads for a second and then says unable to join game session

[Resxt]

gstarr then you did it wrong