My afk button does not return walkspeed to 32 when I turn it off. How do I fix this?

This is the code. The forcefield and walkspeed edit works when you first press it, but when you turn it off, it breaks, plus it keeps your walkspeed at 0 to top it all off.

This is the script:

local On = false

script.Parent.MouseButton1Down:connect(function()
	local player = script.Parent.Parent.Parent.Parent
	if On == false then
		On = true
		player.Character.Humanoid.WalkSpeed = 0
		force = Instance.new("ForceField",player.Character)
	elseif On == true then
		force:remove()
		player.Character.Humanoid.Walkspeed = 32
	end
end)

How do I fix my afk button? I want it to freeze the player's walkspeed and add a forcefield to the player, yet I want that to disable properly when I turn it off. I also want to fix the issue where it breaks after 1 use.

local on = false
script.Parent.MouseButton1Click:Connect(function()
	if on == false then
		plr.Character.Humanoid.WalkSpeed = 0
local force = Instance.new("ForceField")
force.Parent = script.Parent.Parent.Parent.Parent.Character
		on = true
	else
					plr.Character.Humanoid.WalkSpeed = 32
script.Parent.Parent.Parent.Parent.Character.ForceField:Destroy()
on = false

	end
end)

Hopefully this works! Put it in a local script in your button.