Is your squad players or npc?
This sound alot like my arty problems. If you spawn the arty after someone have logged on in MP, or the mission have started in SP, the arty module don't sync with that gun and player.
Oh, and did you use the right module?? It's the normal module, not virtual, you want if you want to get the arty target map.
You don't actually need to sync ANYTHING if you want the arty target map. It sort itself somehow when you have arty and players on the map IF the arty exist before the said player log on/start the mission.