Gui (KeyDown)not working?

In StarterGui I have a ScreenGui called "KeyDownGui". In "KeyDownGui" I have a frame called "Box" and a LocalScript. Inside the LocalScript:

Player = game.Players.LocalPlayer
Mouse = Player:GetMouse()
gui = script.Parent
box = gui.Box
Open = false


Mouse.KeyDown:connect(function(key)
 if (key == "q") then
  if(Open == false) then
   box.Visible = true
   Open = true
 elseif (Open == true) then
  box.Visible = false
  Open = false
  end
 end
end)

I want to be able to press "q" to open the frame(Box) in-game, but in-game the frame does not open up, nothing happens! When I am in Roblox Studio and I go to "Test" at the top and then "Play" it works in there...! If yall would help w/ getting it to work NOT IN ROBLOX STUDIO, that would be awesome! Thanks!

Make a localscript and put it in StarterGui. Then copy and paste this code in it.

thiskey = game.Players.LocalPlayer:GetMouse()
box = script.Parent.Box

thiskey.KeyDown:connect(function(k)
	local key = string.lower(k)
	if key == "q" then
		if box.Visible == false then
			box.Visible = true
		else
			box.Visible = false
		end
	end
end