internet connection

internet connection
All of the solutions previously mentioned should help.

However if you have tried those solutions and are still having issues, you may want to contact your internet provider, and they can help you set your NAT type to open. They will be able to insure your internet is set up properly for online multiplayer gaming.
I've had this issue many times before, because most providers will default you to moderate or strict, unless you tell them otherwise.

:)