Hi shi22dori,
Wordpress alerts 4 abnormal errors when activating the plug-in, have you seen ?
So, i can not install it to confirm you how nulled it.
When i see yours files, access to the "...includes/settings.php" files, line 613 :
$response = wp_remote_get($query, array('timeout' => 20, 'sslverify' => false));
just put '// ' like that :
// $response = wp_remote_get($query, array('timeout' => 20, 'sslverify' => false));
and try to add, so to write just after :
$response = 200;
if it doesn't work, replace 200; by "true;"
That's work for you ?
It's maybe only a part or an approach of the solution, check before if you have really trust in this plugin.
Bye ;-)