Line Unregistered is a error that will display on Polycom phones in the event there is an issue with the registration
Refer to the Master Handset Troubleshooting Guide depending on the make and model to verify
Phone is connected to LAN and obtaining an IP Address
Phone is configured with the correct Boot Server, Server Address, and VLAN ID
Phone has a valid configuration file on either the TFTP Server or the BroadSoft DMS Server