Developer Product script not working?

I took this script from the ROBLOX wiki, and changed it to my needs (Product ID and such) but I will not work. I realize that this script is not made by me, but I would like this to work. What is wrong?

Here is the LOCAL SCRIPT in STARTER PACK:

--LocalScript in StarterPack
-- setup local variables
local buyButton = game.Workspace.BuyButton.SurfaceGui.TextButton
local productId = 21457157

-- when player clicks on buy brick prompt him/her to buy a product
buyButton.MouseButton1Click:connect(function()
    game:GetService("MarketplaceService"):PromptProductPurchase(game.Players.LocalPlayer, productId)
end)

And here is the script in the buybutton thing:

 --Script in BuyButton part
-- setup local variables
local MarketplaceService = game:GetService("MarketplaceService")
local ds = game:GetService("DataStoreService"):GetDataStore("PurchaseHistory")
local productId = 21457157

-- define function that will be called when purchase finished
MarketplaceService.ProcessReceipt = function(receiptInfo) 

    -- find the player based on the PlayerId in receiptInfo
    for i, player in ipairs(game.Players:GetChildren()) do
        if player.userId == receiptInfo.PlayerId then


            -- check which product was purchased
            if receiptInfo.ProductId == productId then

                -- handle purchase
                player.leaderstats["Maple Leaves"].Value = player.leaderstats["Maple Leaves"].Value + 1000
            end
        end
    end 

    -- record the transaction in a Data Store
    local playerProductKey = "player_" .. receiptInfo.PlayerId .. "_purchase_" .. receiptInfo.PurchaseId
    ds:IncrementAsync(playerProductKey, 1)  

    -- tell ROBLOX that we have successfully handled the transaction
    return Enum.ProductPurchaseDecision.PurchaseGranted     
end