A Gui that shows the first time the player plays?

I tryed making a script to save a value to show a gui only the first time a player plays but it doesn't work..... This is Workspace:

function CreateSave(plr)
    if plr:WaitForDataReady() then
        wait(0.03)  
        plr:SaveBoolean("PlayerPlayed_test", false)

        local PlayerPlayedData = plr:LoadBoolean("PlayerPlayed_test")
        local PlayerPlayed = Instance.new("BoolValue")
        PlayerPlayed.Name = "PlayerPlayed"
        PlayerPlayed.Parent = plr   
        PlayerPlayed.Value = PlayerPlayedData
    end
end

game.Players.PlayerAdded:connect(CreateSave)

This is in the Gui, in StarterGui:

function ShowGui(plr)
    if plr.PlayerPlayed == false then
        script.Parent.Visible = true

        script.Parent.MouseButton1Click:connect(function()
            script.Parent.Visible = false
        end)
    end
end

game.Players.PlayerAdded:connect(ShowGui)