local function WaitForChild(parent, childName)
	assert(parent, "ERROR: WaitForChild: parent is nil")
	while not parent:FindFirstChild(childName) do parent.ChildAdded:wait() end
	return parent[childName]
end
local GamePassService = game:GetService('GamePassService')
local PlayersService = game:GetService('Players')
local GamePassIdObject = WaitForChild(script, 'GamePassId')
local function OnPlayerAdded(player)
	if GamePassService:PlayerHasPass(player, GamePassIdObject.Value) then
		if player then
			local PlayerGui = WaitForChild(player, 'PlayerGui')
			local Gui = PlayerGui.SpecialEffectsGui
			Gui.FireButton.Visible = true
			Gui.SmokeButton.Visible = true
			Gui.SparklesButton.Visible = true
		end
	end
end
PlayersService.PlayerAdded:connect(OnPlayerAdded)

No error or warning, located in LocalScript via StarterGui.

Anonymous