Moving part to player within magnitude help?

Hi, I'm trying to create a part with a mesh of a snake. I want this snake to then follow any users within the magnitude of 40 studs and to continue doing so until they've left the magnitude. - For example. They died.

However, at this point in time, the snake won't move and I can't seem to work out why...

while wait(.1) do
	for i,v in pairs(workspace:GetChildren()) do
	if v:IsA("Model") then
		x = v:FindFirstChild("Humanoid")
		if x then
		c = v:FindFirstChild("dontcome") --This is inside certain players to prevent snakes chasing them...
		if c then
			else
		z = x.Parent:FindFirstChild("Head")
		if z then
			if x.Health < 1 then
			else
			if (script.Parent.Head.Position - z.Position).Magnitude <= 40 then
			script.Parent.Humanoid:MoveTo(z.Position)
			else
			wait(0.01)
		end end
		end
	end end
	end
	end
end

Everything inside the "Snake":

https://gyazo.com/5de683e395307fd7f43f8064aa6d86b2

There are no errors in the output either.

Thank you.

while true do wait()
	for _, v in pairs(workspace:GetChildren()) do
		if v.ClassName == "Model" and v:FindFirstChild("HumanoidRootPart") then
			local plr = v
			if script.Parent.Humanoid.Health > 0 then
				local head = plr.Head
				if math.abs(math.abs(head.Position).Magnitude)-(math.abs(script.Parent.Head.Position)).Magnitude) < 41 then
					script.Parent.Humanoid.WalkToPoint = Vector3.new(head.Position)
				end
			end
		end
	end
end

Easier to understand, the math.abs is the absolute value, if the players heads magnitude is less than or equal to 40 to the snake then the snake moves to the head. Don't forget to add vectors.

I am not willing to read what the guy above wrote... But this is how I would do it.

Alright there, edited again.