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Yealink T4x Series IP Phone Displays No Service

Symptom

Yealink T4xG series (T41P/G,T42G, T46G,T48G) and Yealink T4xS series (T48S,T42S,T41S) phone LCD display shows the message "No Service". There is no dial tone, and you are unable to make or receive calls.

Applies To

  • Yealink SIP-T41P/G 
  • Yealink SIP-T42G 
  • Yealink SIP-T46G 
  • Yealink SIP-T48G
  • Yealink SIP-T41S
  • Yealink SIP-T42S
  • Yealink SIP-T46S
  • Yealink SIP-T48S

Resolution

Note: 8x8 is not responsible for any issues or problems it may cause for devices purchased elsewhere.
These are tested for use on 8x8 purchased Yealink devices.
  1. In cases where the phone had been properly working for a long time and is only suddenly afflicted with these error messages, power cycling your network is often able to clear it up.
  2. Next, check if the device is on the recommended firmware.
    • Check the firmware of the phone by pressing OK.
    • Confirm the version needed. See Check Firmware Version on Yealink T4x Series. 
    • Another way to check the version is via the web GUI by obtaining the IP address from the phone or the Client list table from your router.
      • Log in to the phone's IP address (default user/password: admin/admin).
      • Navigate to Status > Status > Firmware Version.
        Firmware.PNG
  3. If the device is not on the same firmware, either newer or older; flash it to the recommended version.
    • Request to for the correct firmware file, you can confirm the version needed see What is the recommended firmware for 8x8 phones and analog adapters?
    • Next, go to Settings > Upgrade > Select and Upgrade Firmware.
    • Click Choose File choose the firmware file saved previously, and press Upgrade.
    • The phone will reboot and update it's firmware, once done proceed to the next step.
  4. Make sure to provision the phone to 8x8 server.
    • Go to Settings > Auto Provision.
    • Enter Server URL: https://ylcfg.8x8.com/yealink/
    • Click Autoprovision Now.
    • The phone will reboot twice and once booted, will have the chance to activate.
Other helpful network troubleshooting:
  • Swap out the Ethernet cord connecting the phone to the network for a different one (to see if a faulty cord might be the issue).
  • Is the phone connected to a wall jack? If so, try connecting it directly to a networking device (router or switch).
  • If the phone is connected to a networking device, try plugging it into a different port on the device (to see if a faulty port is the issue).
  • If accessible, review the firewall/router settings and be sure to disable the following:
    • SIP-ALG
    • SPI
    • Firewall

Cause

  • Phone has an incompatible firmware.
  • Phone is unable to successfully register a SIP account with our services.