Yealink T54W: Phone Not Registering or Shows 'No Service'

If your Yealink T54W displays "No Service," "Unregistered," or shows a registration error, here's how to troubleshoot it. What registration means: The T54W needs to register with your phone system's SIP server to make and receive calls. If it can't reach the server, or the credentials are wrong, it shows as unregistered and won't work. Step 1: Check the network connection Look at the back of the phone — the Ethernet cable should be plugged into the port labeled "Internet" or "LAN" (not the PC port). Make sure the cable is seated firmly. The LED next to the port should be lit. If using Wi-Fi: check the Wi-Fi icon at the top of the phone screen is showing connected. Step 2: Reboot the phone Press Menu > Advanced > Reboot > Confirm. Or unplug the power adapter (or Ethernet cable if PoE-powered), wait 15 seconds, and reconnect. The phone goes through a startup sequence and attempts to re-register. Watch the screen — it should say "Registering..." then show the phone number/extension if successful. Step 3: Check if internet is working From another device on the same network (a computer or phone), confirm the internet is working. If the whole office has no internet, the phones won't register until connectivity is restored. Step 4: Check SIP ALG on the router SIP ALG is a router feature that frequently causes VoIP registration failures. If phones were working and suddenly stopped after a router change or reset, SIP ALG may have been re-enabled. Contact us to check and disable SIP ALG. Step 5: Check the phone's SIP account status Press Menu > Status > More... > Accounts. This shows each registered SIP account and its status (Registered or Failed). If it shows Failed, the credentials or server address may be wrong — contact us to re-provision the phone. Step 6: Factory reset as a last resort Only do this if we instruct you to — a factory reset wipes all settings and the phone will need to be re-provisioned by us. To factory reset: Press and hold the OK button for 6–7 seconds until a confirmation prompt appears > press OK to confirm. Contact us immediately at (269) 261-0269 if phones are down — this is a business-critical issue.