WordPress allows you to install plugins from external systems, which are normally paid plugins with advanced functionality. As these plugins can't be directly updated via the standard system, they generally require a license key to be added to ensure you have a valid subscription. This subscription is important to maintain, as the plugin developers release regular updates to fix bugs, add new features and most importantly fix any potential security issues (if they occur).
You may see that an update is available through your WordPress Admin area, however it won't automatically update like regular plugins without the license installed. This presents as a potential security risk and therefore should be addressed immediately.
If you have a Managed WordPress subscription with Conetix, we don't cover the cost of these plugins and it remains the responsibility of the site owner to organise licenses. Once licenced however, Conetix can maintain the updates as normal.