When a Yealink IP Phone displays the words “No Service” it means the device was unable to successfully register to our network.
In cases where the phone had been properly working for a long time and is only suddenly afflicted with these error messages, a rebooting the device often will normally clear up the issue. If not you are going to want to investigate the local area network (LAN) for possible issues.
Make sure the device has a valid local IP address. This can be done by pressing the OK button on the phone which will cause it to display it’s current network data.
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