Why is my Regeneration script not working?

I have changed allot of things in the script, but it is still not working, there is no error Output so I don't know what the problem is, but, the problem is that it is not respawning an NPC, and when it does, the player just dies, or falls through the baseplate, so it repeatedly loops over and over again, here is the script;

repeat wait() until script and script.Parent and script.Parent:FindFirstChild("Zombie")
print("Respawned")
wait(1)
repeat wait(.2)
if script.Parent.Zombie.Health <= 0 then
print("Respawning")
local Respawn = script.Parent:Clone()
Respawn.Parent = game.Workspace
Respawn:MakeJoints()
script.Parent:Destroy()
end
until nil

Make sure your NPC is a Humanoid not a Zombie and clone it and make sure it's in workspace, for the other one you can delete it.