AShop doesn't require that you make any special settings in the 2CheckOut admin panel.
AShop uses the single item purchase method to submit multiple products at once.
On the last page after 2CheckOut payment there is a "Finish order" button that must be pressed to send the order to AShops order.php script. The page clearly states that you must press the button to complete the order. If you recieve an occasional payment that is not recorded within AShop, it could be caused by the customer not clicking the Finish Order button.