Oct 7, 2011 Question: How can I check out the Registration Status of my Phone? Resolution: Please check => here <=
Above explains how you can check the registration status of the phone.
If it is no longer registered to your SIP server you will not be able to make inbound calls.
Maybe you received a new IP and the NAT settings do no longer work?
Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.
Polycom Global Services
Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels. Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's