My enemies after I kill them won't return to the level?

Help Requests
1

When I kill my Yurei, (Ghost) it doesn’t return, it disappears from the editor and disappears from the level, I am really confused… I probably missed something really obvious. :confused:

2

reload the level… it will return

3

but I can just go through the level without enemies after I killed them, making the level incredibly easy…

4

ok now i fixed it, it now it spawns multiple enemies