It seems that when a group of people want to play a non-official map, no one except the host should have the map unless everyone has the map for the game to connect. In order for the game to work, everyone except the host must delete the map from their RA2 folder prior to the game starting. The alternative is to get the map in your RA2 folder. This is why I will release a mpa pack, so everyone can have access to it. This way, maybe everyone can play.
“I am the punishment of God...If you had not committed great sins, God would not have sent a punishment like me upon you.”