VoIP Phone Won't Register — No Service, No Lines, Blank Screen

A phone that won't register has a problem in one of three layers: power and network, provisioning (can it fetch its config?), or SIP (can it reach the server?). Work down the list — the first two steps resolve the majority of cases.

1. Power and network

• Reseat the network cable in the phone's LAN port (not the PC port), and confirm the port is PoE or the power adapter is attached.
• Reboot: unplug, wait ten seconds, reconnect. Full boot takes 2–4 minutes.
• Does the phone get an IP address? (Check its Status menu.) If not, the problem is the switch/DHCP, not the phone system.

2. Provisioning

• In the portal, check the device's Last Seen. A recent timestamp means the phone reached provisioning and the issue is SIP; never-seen means it can't fetch config at all.
• Verify the MAC in the portal matches the label on the phone exactly — one transposed character is the classic cause for a brand-new phone.
• Phone previously used with another provider? It may still point at the old provisioning server. Factory-reset it (see its Device Library page), and it will pick up Signal's configuration.

3. SIP and firewall

• Confirm outbound TCP 5061 (TLS) is allowed and SIP ALG is disabled on the router — ALG corrupts registrations intermittently, which presents as phones that register and then vanish.
• If several phones at one site are down together, suspect site network or ISP, not the individual devices.

Escalating

Include the MAC address, the Last Seen timestamp from the portal, the site, and what the phone's screen shows. Those four facts usually make it a one-touch fix.

Related articles

• VoIP network requirements
• Adding a phone