License problem - DOMAIN_REQUIRED error message
When you see a DOMAIN_REQUIRED error message showing up, when you do a license related action, the problem is given by, that something is set up wrongly on your website about it's url. Usually it's in the site's configuration, but sometimes there are plugins/extensions changing the url variables or constants wrongly. Here are some common mistakes:
In the config.php file the $url variable has a wrong value. It should contain the full url to your installation folder, for example:
public static $url = 'http://example.org/html/';
In the wp-config.php file there were changes made related to the url of your website. Usually it is the wrong definition of the WP_CONTENT_URL constant. This constant should contain the full url of your website pointing to the wp-content folder:
If you don't have this constant defined, then you could try to define it, which might fixes your problem.
You probably have the $live_site variable given in your configuration.php file. If you do, make sure, that you have the full url of your website given:
public $live_site = 'http://example.com/';
If you don't have this variable defined, then you could try to define it, which might fixes your problem.