Could someone tell me what I'm doing wrong in my script to make certain people have a GUI?

local CoolBoy = {
    3179316 ,31862508,
}

local Player = players.LocalPlayer
local Gui = Player.PlayerGui.SliderGui
local found = false

for i =1, #CoolBoy do
    if CoolBoy[i]== Player.UserId then
        Gui.Visible = true
        found = true
    else
        if not found then
               Gui.Visible = false
        end
    end
end

Notes: This is all in a LocalScript inside of StarterPlayer>StarterPlayerScripts, the GUI is called SliderGui and is in StarterGui. Alright thanks if you can help.

is players defined? If it isn't, there's your problem.

Another thing that will probably help is replacing line 6 with:

local Gui = Player:WaitForChild("PlayerGui"):WaitForChild("SliderGui")