Oh, now I'm getting error 018-0512. Apparently it has something to do with one of these things:
--This error code typically indicates an issue communicating and matchmaking with other players.
--This is often caused by network firewalls blocking necessary network traffic.
--This can be caused by your network, or the network of the person you are connecting with. If these steps do not resolve your connection issue, have your friend try them as well.