WooCommerce License ManagerWooCommerce License Manager is a WordPress plugin that allows you to easily sell a license key, a gift card PIN code or a license of your digital product with a license key that you pre-defined or automatically.
New features in version 4.0
-Added option to automatically change the status of expired license key.
-Better back-order support: Add more options to the order page so you can change the keys one by one or set new ones for existing orders.
Demo here: https://codecanyon.net/item/woocommerce-license-manager/16636748