OWN SERVER PUBLISHERS ONLY
This error is displayed when registering a customer account if you have configured the server URL incorrectly.
Login to the master account and go to master-> settings-> modify server url and enter:
http://myservername.com/ll-master/ (where myservername.com is your domain name).
If the error continues, try registering using the license link on the customer account (rather than the one sent by email) – either save it to disk or open it directly from the admin panel.
If that still does not work, and other customer accounts register fine, then remove the customer account and re-create it.