last time i had that it was because i was trying to run maps that dont work with/without particular mods.

for me it was a solar System  without the 7ds mod if i remember.

it also happens with map designer maps in galaxyforge folder & galaxyforge maps in mapdesigner folder, and also maps with more players that home planets, and as astax suggested when all players/ais are on the same team, basically there needs to be a homeworld for each player and at least two teams with the map in the correct folder with the right mods enabled.

personally when I create my maps I use the weighted & random planets unless I want/need a particular planet type at a particular location. that way the map will play in all mods for the sins version

harpo