WPML has a tendency to be a bit flaky with their keys and overnight your WPML site may become unregistered.
This is a pain because, in order to re-register the site again and get access to updates, you have to log in to WPML, find the key, navigate back to WordPress, update the key....its a drag.
However, with the snippet below, adding it to the wp-config.php file, you can override the license key in the database by defining a global variable called: OTGS_INSTALLER_SITE_KEY_WPML
So just add this to your wp-config and you will be set.
################################
// hard code WPML site key in wp-config.php
// https://www.jucra.com/whmcs/knowledgebase/173/
// see: https://wpml.org/faq/install-wpml/#registration-using-php
################################
define( 'OTGS_INSTALLER_SITE_KEY_WPML', 'site_key' );
Another good use for this is if you have a dev server and a production server, you can define two different license keys for each so when swapping the files between the two servers you don't need to keep updating the key in the database.
;o)
