KeyDown Function is giving no errors but doesn't emit a function?

player = game.Players.LocalPlayer
mouse = player:GetMouse()
gui = script.Parent
Open = false

function PressE(key)
    if (key == "e") then
        if (Open == false) then
            for i = 1,0,-0.1 do
                gui.BackgroundTransparency = i
            end
            Open = true
        elseif (Open == true) then
            for k = 0,1,0.1 do
                gui.BackgroundTransparency = k
            end
            Open = false
        end
    end
end

mouse.KeyDown:connect(PressE)

This script doesn't label any errors nor does it do anything. Please fix!