Yealink SIP-T21 - Manual (Page 127)

Troubleshooting
117
This chapter provides general troubleshooting information to help to solve the problems
you might encounter when using your SIP-T21P/SIP-T21 IP phone.
If you require additional information or assistance with your new phone, contact your
system administrator.
Why is the LCD screen blank?

Ensure that the phone is properly plugged into a functional AC outlet.

Ensure that the phone is plugged into a socket controlled by a switch that is on.

If the phone is plugged into a power strip, try plugging it directly into a wall outlet
instead.

If your SIP-T21P IP phone is powered from PoE, ensure you use a PoE-compliant
switch or hub.
Why does the phone display “Network Unavailable”?

Ensure that the Ethernet cable is plugged into the Internet port on the phone and
the Ethernet cable is not loose.

Ensure that the switch or hub in your network is operational.

Contact your system administrator for more information.
Why does the phone display “No Service”?
The LCD screen displays “No Service” when no SIP account registers successfully.
Why doesn’t the phone display time and date correctly?
Check if you have configured the phone to obtain the time and date from the SNTP
server automatically. If the phone fails to connect the SNTP server, configure the time
and date manually.
How do I find the basic information of the phone?
Press the OK key when the phone is idle to check the basic information of the phone,
such as the IP address and firmware version. For more the basic information, refer to
Phone Status on page 13 .