Dev product script not printing anything?

Hey, trying to make a dev product for my game but it just doesn't work. No errors, no prints, nothing.

Here's the code -

ShekelsGiven = script.Parent.AmountGiven

ProductID = 31831485

game:GetService("MarketplaceService").ProcessReceipt = function(receiptInfo)

    for i, player in ipairs(game.Players:GetChildren()) do
        print'1'        
        if player.userId == receiptInfo.PlayerId then
        print'2'
            if receiptInfo.ProductId == ProductID then
                print'3'
                if receiptInfo.CurrencyType == Enum.CurrencyType.Robux then
                    print'4'
                    player.ShopValues.Shekels.Value = player.ShopValues.Shekels.Value + ShekelsGiven.Value
                print'5'

                end

            end

        end

    end
print'6'    
                return Enum.ProductPurchaseDecision.PurchaseGranted

end

Thanks for reading