License activation is possible only for those who have purchased the plugin through the sales page on CodeCanyon.
Apart from being sold on the marketplace, Convert Plus is also bundled with various WordPress themes like The7, X Theme, Avada, etc. that allow you to use the plugin. The license key you get while purchasing the theme, is meant to activate the theme itself and not the plugins that come along.
The bundled version of Convert Plus can be used easily with all necessary features and around 30+ integrations. There are just 5 add-ons (which include WP Registration Form, WP Comment Form, Contact Form 7, Connects Woocommerce, Visual Composer add-on ) we offer as incentives to users who buy a direct license.
Apart from these addons, our direct customers get access to immediate updates (which often gets delayed in a bundled plugin due to the theme authors reviewing and forwarding an update) and direct support from our developers.
In case you wish to gain access to all of these, you will need to buy Convert Plus directly from CodeCanyon and get your own license.