Sit detection local script not working?

This local script doesn't make the surface GUI children visible?

	game.Players.LocalPlayer.Character.Humanoid:GetPropertyChangedSignal("Sit"):Connect(function()
	if game.Players.LocalPlayer.Character.Humanoid.Sit == true then
		script.Parent.Screen.SurfaceGui.ScrollingFrame.Visible = true
		script.Parent.Screen.SurfaceGui.Laptop.Visible = true
		else
		script.Parent.Screen.SurfaceGui.ScrollingFrame.Visible = false
		script.Parent.Screen.SurfaceGui.Laptop.Visible = false
		end
	end

This is my finished script ,it still doesn't work?

local isSitting = false
   game.Players.LocalPlayer.Character.Humanoid.StateChanged:Connect(function(old, new)
	if game.Players.LocalPlayer.Character.Humanoid.Sit then
	
		script.Parent.Screen.SurfaceGui.ScrollingFrame.Visible = true
		script.Parent.Screen.SurfaceGui.Laptop.Visible = true
		else
		script.Parent.Screen.SurfaceGui.ScrollingFrame.Visible = false
		script.Parent.Screen.SurfaceGui.Laptop.Visible = false
		end
	end

local plr =  game.Players.LocalPlayer
local char = plr.Character
local hum =  char:WaitForChild("Humanoid")

hum.HumanoidStateChanged:Connect(function(old, new) --Fires when a humanoid's state changes
	if hum.Sit then  --If  we're sitting...
		--code
	elseif not hum.Sit then  --If we're not...
		--code
	end
end)
		

good explanation how to properly script this can be found here https://developer.roblox.com/en-us/api-reference/event/Humanoid/StateChanged