STEP 1: Download Lastest Configuration:
1.) Select "Menu" from your main screen
2.) Select "Basic" from the Main Menu
3.) Select item "12. Update Configuration" from Basic Settings
4.) Select "OK" from the "Warning...Provision now?" screen.
STEP 2: Reboot Phone
1.) Select "Menu" from your main screen
2.) Select "Basic" from the Main Menu
3.) Select "11. Reboot" from the Basic Settings menu
4.) Select "OK" from the "Warning...Reboot the phone?" screen
STEP 3 (Optional if previous steps do not fix the issue): Factory Reset
1.) Depending on your phone model, press and hold the appropriate button for about 15 seconds until you are prompted to factory reset.
Yealink T34 (Small Screen)
Yealink T57 (Larger Screen)
Yealink T85 (Touchscreen)
2.) Select "OK" and wait for the phone to reboot.