Why won't my script recognise a Gui in my PlayerGui folder?

The code I have is

function Clicked(Plr)
if script.Parent.Parent.monitor.screen.SurfaceGui.login.Visible == true then
    Plr.PlayerGui.deskone.login.Visible=true
 else
    Plr.PlayerGui.deskone.welcome.Visible=true
end
end

script.Parent.ClickDetector.MouseClick:connect(Clicked)

I want to make it so when the player clicks the part it makes the ScreenGui in the PlayerGui folder visible however when I play the game it gives me the error that 'deskone is not a valid member of PlayerGui' when in my player folder it has PlayerGui.deskone when looking at the workspace.

Thanks for any help.