BNW - can't get MP to work

[CDUB4401]

I'm on a LAN with my buddy via a switch. We dont have an active internet connection, just the lan. We can transfer files between pcs so we know the connection is good. Yesterday, we tried to play with him hosting and I could not see his game in the list. But I could host and he could join. We played for a couple hours and I saved the game. Today we tried to continue our game. He can't see the game in the list when I try to host. He can't see the game in the list if I try to host a new game. I can't see any of his games in the list if he hosts. We turned off all firewalls and antivirus and now I can see his game when he hosts but he can't see my game if I host. What is wrong? Please help.