I recently started playing Sins again with a friend of mine. I went and made a map in Galaxy forge to for us to try out. However despite us both having the file in our documents/ironclad/sins/galaxy forge and it being the exact same file we are told that he does not have the files needed to join the game.

Out of curiosity I created another galaxy forge map with the standard layout of two planets, I sent him the map, and it let him join the game. So I figured perhaps the problem was that I made the original map when I had 1.87 installed.

I made a second map, similar in design, and sent it to him, once again installing it in the same place. And again. He couldn't join.

Finally after getting fed up looking for a fix for this issue I went and edited one of the base-game map files to raise the starting resources. I sent him the file. And we got a similar error. The odd thing about this is all of the maps have been 100% playable in singleplayer, however when he tries to join me it won't let him, and vice versa. 

Anyone have any insight or suggestions? I've hit a wall, and it's really starting to heavily effect my enjoyment of the game at this point.