This error typically occurs when a user already has a registered server.
VyprVPN for Business users will need to add a VyprVPN Licensed Server license to their account in order to register a server. When on a VyprVPN for Business account, there is no limit to how many concurrent VPN connections the server can have.
Individual VyprVPN users can register one server, with that server allowing 2 concurrent VPN connections.
To remedy this error, follow the steps here - How do I deregister a server
If that does not resolve the issue, or you haven't previously registered a VyprVPN Server, reboot the server from the System Settings section in the web administration panel and try again after it comes back online.
If you need any further assistance, please contact our 24/7 Customer Success Team, who would be glad to assist.