Seeing this is typically an indication of networking issues. The overall article that deals with NAT issues, can be found below: https://www.bungie.net/en/Help/Article/11931 If, typically you have no problem, and this just popped up, though, I recommend power cycling your networking equipment (unplug modem and router for a few minutes). I see the lack of matchmaking Pop up on occasion - a quick recycle of my router always takes care of it.