Why wont this work?

I made a script that on "f" pressed turns on SpotLight, the problem is when I use key == "f" it doesn't work and when I use key:byte() == 50 (etc.) it does.. Here's script

script.Parent.ChildAdded:connect(function()
    if mouse == nil then
        Player = game.Players.LocalPlayer
        mouse = Player:GetMouse()
    end
mouse.KeyDown:connect(function(key)


    local Left = script.Parent.Parent.Lights.FL.FLL
    local Right = script.Parent.Parent.Lights.FR.FRL
    key = key:lower()
        if key == "f" and Left.Enabled == false then
            Left.Enabled = true
            Right.Enabled = true
        if key == "f" and Left.Enabled == true then
            Left.Enabled = false
            Right.Enabled = false
        end
        end
end)
end)