Sometimes new orders are not reflected in the order list even though the payments are finished. It mostly happens that we can't receive the notification from the payment service (eg: PayPal) due to network problems. In this case, you can search and retrieve the missing orders. Just go to Sales->Orders, choose 'Missing orders' under the 'Status' and then click the 'Filter' button. After searching, you can change the status to what ever you want.