Desk Phone / VoIP Not Working (No Dial Tone or Not Registering)

Category: VoIP & Phones · Audience: Customers & Technicians · Est. time: 10–20 min

Summary

VoIP desk phones make calls over the network/internet. "No service," "Not registered," or a dead phone is usually power/network or a registration issue.

Symptoms

• Phone screen shows "Not Registered" / "No Service" / "Registering…"
• No dial tone; can't make or receive calls
• Phone screen blank/off

Solution

1. Check power. Most VoIP phones are PoE (powered by the network cable from a PoE switch). No screen = no power → check the cable is in the phone's LAN/PoE port and the switch port is live. A PoE injector, if used, must be powered.
2. Check the network cable. Re‑seat the cable at the phone and wall/switch. If the phone has two ports (LAN and PC), the wall/switch goes to LAN, the computer to PC.
3. Reboot the phone. Unplug the network/power for 20 seconds and reconnect. It should re‑register within a minute.
4. Is it just one phone or all?

• One phone → local (power/cable/that phone).
• All phones → the internet is down (see the Sophos internet article) or the phone system/SIP provider has an issue.

1. Check internet. VoIP needs working internet. If the office internet is down, phones won't register — restoring internet fixes them.
2. Registration details (Technician). In the phone's admin/web UI, confirm the SIP account is provisioned and the server/registrar is reachable. Re‑provision if it lost config after a factory reset or firmware change.

If that doesn't work

• Swap the phone's cable/port with a known‑good one to isolate cabling vs phone.
• Note whether calls fail outbound, inbound, or both.
• Escalate to BBN Support (or the phone provider) with the extension, the on‑screen status, and one‑phone vs all.

Prevention

• Keep phones on PoE with spare ports; ensure the internet link is reliable (VoIP is sensitive to outages).