My Phone Won't Register — Troubleshooting Guide

Introduction

When a desk phone shows "No Service", "Registration Failed", or a similar error, it cannot make or receive calls. This guide covers the most common causes and how to fix them.

Quick checklist

Run through these checks first — most registration failures have a simple cause:

1. Is the network cable plugged in? Check both ends — the phone and the switch port.
2. Does the phone have an IP address? Press OK on a Yealink to see the IP. If it shows 0.0.0.0, the phone has no network connection.
3. Are the SIP credentials correct? Even one wrong character prevents registration.

Check the SIP credentials

The most common cause of registration failure is wrong credentials. Verify each field:

1. On the phone's web interface (browse to the phone's IP address), go to Account > Register.
2. Compare each field against the extension in the PBX portal (Extension and Trunk > Extension, click the extension):

1. If the password looks correct but registration still fails, click Generate on the Registration Password field in the PBX to create a new password, enter it in the phone, and try again.

Check DNS resolution

The phone must be able to resolve your PBX domain. Test by:
1. Temporarily replacing the Server Host on the phone with the PBX IP address.
2. If the phone registers, the issue is DNS — check the phone's DNS server settings.

Check for firewall or NAT issues

Cloud Edition is designed to work through NAT automatically, but firewalls can block SIP traffic:

• SIP uses port 5060 (UDP) by default. Ensure your router/firewall is not blocking this.
• Some routers have a "SIP ALG" setting that interferes with SIP traffic. Try disabling SIP ALG on your router.

Phone was working before — sudden failure

If the phone was working and stopped:
- Password changed? Check if anyone regenerated the Registration Password in the PBX.
- PBX URL changed? Cloud Edition URLs are permanent, but if the PBX was migrated, the domain may have changed.
- Factory reset on the phone? If the phone was reset, all settings are gone — re-provision or re-enter credentials.

Check the PBX status

From the admin portal:
1. Go to the Status Centre (Dashboard).
2. Find the extension — if it shows offline, the registration is not reaching the PBX.
3. Go to Reports > System Log for SIP REGISTER messages to see exactly what error the PBX is returning.

Tips

• After correcting credentials on the phone, wait 30–60 seconds for registration to complete.
• Yealink phones can be rebooted from their web interface: Settings > Upgrade > Reboot.
• If multiple phones on the same site stopped registering simultaneously, the issue is likely the network or firewall, not the phone configuration.

Summary

Most registration failures are caused by wrong SIP credentials or network issues. Check the credentials first, then DNS, then firewall. Contact X2Comms support if the issue persists after these checks.