tbh, PvP has certain times of the day, where it's not being used. So no matter what you do, you wouldn't find a game anyway. The Port forwarding would cause the game not to be created. It would not prevent you from finding other players.
I've had this issue occur as well. I don't think it has anything to do with ports just seems like a bug. I would suggest going to Sparta and then clicking the arena building to start a PvP match. That always works for me.