Starcraft Broodwar editor: unit's wont stay in the map!?

Hi, so I was trying to make a map in StarEdit starcraft editor the other day... Problem is: when I place the units for any player, they won't stay in the map when I test it. Everything dissappears, there is only a Command Center/Hatchery/Nexus with 4 SCVs/Drones/Probes on the starting location when I start the map in game.