Most of the time when I start a matchmade mission replay, the other agents and I are unable to enter the mission area. For instance, right now we are just sitting in front of the Broadway Emporium mission with the gates of this mall closed. Does anyone know what we're missing here? Do we have to have all four members or something? I can start it solo, but I'm trying to finish a couple achievements that require I be in a group. Any ideas?