If your computer is behind a firewall

In a LAN, Nuendo uses the UDP port 6990 to establish communication with the other computers. Over the internet however, Nuendo does not use this port. Instead, connection and communication is established and handled via TCP/IP messages sent to the TCP ports 6991 and 6992.

This means that the TCP ports 6991 and 6992 must be open on all computers. Firewalls may block messages to these ports, thus making connection impossible. Consult the documentation for your firewall (or operating system) for information about how to open ports – or contact your network administrator.