Why wont my script work? [Not solved]

I have got this for my developer product to add 5000 cash but it wont work please help.

id = 20566241 --dev product id

script.Parent.MouseButton1Click:connect(function()
    game:GetService("MarketplaceService"):PromptProductPurchase(game.Players.LocalPlayer, id)
    local MarketplaceService = Game:GetService("MarketplaceService")
    local ds = game:GetService("DataStoreService"):GetDataStore("PurchaseHistory")
    MarketplaceService.ProcessReceipt = function(receiptInfo) 
        if game.Players.LocalPlayer.userId == receiptInfo.PlayerId then
            if receiptInfo.ProductId == id then
                game.Players.LocalPlayer.leaderstats.Cash.Value = game.Players.LocalPlayer.leaderstats.Cash.Value + 5000
            end
        end 

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

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

The error is that it wont give me the 5000 cash and I have to reset to buy it again.