It is not possible to update custom (paid) plugins and/or themes in Plesk in WordPress > example.com > Updates, with the following warning:
Selected items were updated with errors:
-Unable to update plugin 'all-in-one-seo-pack-pro_3.3.4_2', details: One of the common causes of this error is plugin or theme requiring a license to be updated. Log in to WordPress admin dashboard and try updating this plugin or theme there to discover more details about the issue.
License required for the plugin/theme updates.
WordPress Toolkit can update paid plugins & themes if these updates are available in the WordPress admin area.
However, plugins and themes that require a license for automatic update will cause the above warning message to show when trying to update them via WordPress Toolkit without a license.
Install and activate the corresponding license for the plugin and/or theme to allow automatic updates.