Why does this script work only on an empty baseplate, but not in another game?

The coding seems correct, however it refuses to work in game, I tested it in a baseplate and it somehow worked but the scripts are exactly the same in both the baseplate and game.

This script is supposed to list the players points on a global leaderboard as a GUI.

local ODS = game:GetService("DataStoreService"):GetOrderedDataStore("Points")
local Pages = ODS:GetSortedAsync(false,10)
local Data = Pages:GetCurrentPage()
local GUI = game.StarterGui.LeaderboardUI

game.Players.PlayerAdded:Connect(function(plr)
	local New = Instance.new("Folder")
	New.Name = "leaderstats"
	New.Parent = plr
	local Stage = Instance.new("NumberValue")
	Stage.Name = "Stage"
	Stage.Parent = New
end)

game.Players.PlayerRemoving:Connect(function(plr)
	local Stage = plr.leaderstats.Points
	if Stage then
		ODS:IncrementAsync(plr.Name,Stage.Value)
	end
end)

local function Update()
	local succ,err = pcall(function()
		local Template = GUI.Template
			for i,v in pairs(GUI.MainFrame:GetChildren())do
				if v:IsA("Frame") then
					v:Destroy()
				end
			end
		for a,k in pairs(Data)do
			local PlayerName = k.key
			local PlayerStage = k.value
			local NewTemp = Template:Clone()
			NewTemp.Name = PlayerName
			NewTemp.FrameName.Text = PlayerName
			NewTemp.FrameValue.Text = PlayerStage
			NewTemp.Visible = true
			NewTemp.Parent = GUI.MainFrame
		end
	end)
	if err then
		warn("An error has occured when trying to update the leaderboard: " .. err)
	end
end

Update()

spawn(function()
	while wait(60*3) do
		Update()
	end
end)

What could be causing this? Please help!

Note there are two scripts here, local and server...This is assuming your GUI is in RS. This is an example of the remote needed for client/server communication for FE. This is in addition to your script obviously.

-- LocalScript 
local remote = game:GetService("ReplicatedStorage").YourGui -- name it


remote.OnClientEvent:Connect(function()
    script.Parent.Visible = true
end)

-- Server
local remote = game:GetService("ReplicatedStorage").YourGui

local function click(player) 
  remote:FireClient(player) -- fire to client
end 

script.Parent.ClickDetector.MouseClick:Connect(click)