You are using "GROUP" respawn (I'd advise you to use "GROUP" rather than 4 as the value of respawn, since it is easier to recognise and wouldnt' have required me to look it up). Respawn is enabled correctly though, but in "GROUP" respawn, you respawn only into other playable characters in your group. In your mission, you have 3 playable characters, but each in different groups of AI, so you have noone to spawn into. You either want to use a different respawn type (e.g. "BASE") so that you can respawn into the same man indefinitely, or you need to make all the soldiers playable, so that the players can respawn inside their groups.