Why don't ProductPurchase give me money from the sales?

I tried following the wiki and example place but there still must be something wrong, because when someone buys the developer product in-game, I don't ever receive payment.

This script is in the Workspace:

MarketplaceService = Game:GetService("MarketplaceService")  


local ID = 19690897   
local PurchaseHistory = game:GetService("DataStoreService"):GetDataStore("PurchaseHistory")  

    MarketplaceService.ProcessReceipt = function(receiptInfo)   
        local playerProductKey = receiptInfo.PlayerId .. ":" .. receiptInfo.PurchaseId  
        if PurchaseHistory:GetAsync(playerProductKey) then  
            return Enum.ProductPurchaseDecision.PurchaseGranted --We already granted it.  
        end  
        -- 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 (required, otherwise you'll award the wrong items if you're using more than one developer product)  
                if receiptInfo.ProductId == ID then  
                    -- handle purchase. In this case we are healing the player.  
                    player.leaderstats.Points.Value = player.leaderstats.Points.Value + 25000  
                end  
            end   
        end  
        -- record the transaction in a Data Store  
        PurchaseHistory:SetAsync(playerProductKey, true)      
        -- tell ROBLOX that we have successfully handled the transaction (required)  
        return Enum.ProductPurchaseDecision.PurchaseGranted       
    end

And this is used to prompt the purchase after pressing a gui button: MarketplaceService:PromptProductPurchase(player, 19690897)