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Knowledge Base & Operational DocumentationWhy Does a VoIP Phone Display “Not Registered” After a Network Change?
A phone may lose registration after a network change because of VLAN, DHCP, firewall, DNS, or provisioning differences. It may still power on and show a user’s name while being unable to receive calls.
What to check
Check device IP, voice VLAN, provisioning server, DNS, SIP reachability, firewall rules, and registration logs. Compare a working phone on the same network and note whether the issue follows the device or port.
Recommended next step
Correct the network or provisioning setting at its owner and validate registration and test calls both ways. Avoid opening broad signaling ports without confirming provider requirements.
How Informatix Systems can help
Informatix Systems provides VoIP and network communications services. We can assess the affected setup, trace dependencies, and help plan a practical improvement. Contact us with the platform involved, when the issue began, and non-sensitive error details.