If you sell a network license where each order can contain a different quantity of licenses, it is not possible to work with uploaded keys. You have to create a Serial Number Key which is different per order and includes the quantity of licenses ordered.
After the order process, an automated Licence Generator is invoked by the shop system. The automated Licence Generator uses the quantity from the order and a special definition file to generate a Serial Number key which includes the number of licenses for a network license.