Under certain circumstances, a login/registration of the VoIP telephone to the telephone system may fail in rare cases during configuration and operation. The telephone is not usable. The Service Desk cannot resolve the issue after consulting remotely.

If resolution via remote support is not possible through the Service Desk, the VoIP phone may need to be reset to factory settings locally to re-register it with the PBX.
The procedure varies depending on the phone type and should only be carried out in consultation with ZIH.

Standard Phone Cisco CP-7841

1. Unplug the LAN cable
2. Wait 5 seconds.
3. Press and hold # and plug the phone back in.
4. Release the # only when the Headset and Speaker buttons are lit.
   Note: On earlier hardware versions, the Mute button lights up along with the Headset and Speaker button.
   Wait for the Mute button to turn off to release the # Key.
5. Enter the following key sequence: 123456789*0#
   The light for the Headset button turns off after you press the 1 key. After you enter the key sequence, the Mute button lights.
6. The phone resets.

Caution: Do not power down the phone until it completes the factory reset process, and the main screen appears.

Phone Cisco CP-8851

1. Unplug the LAN cable
2. Wait for 5 seconds
3. Press and hold # and plug the phone back in.
4. Release the # only when the Headset and Speaker buttons are lit.
   Note: In some hardware versions, the Mute button also lights along with Headset and Speaker buttons when you plug the phone back in. In that case, wait for all of them to go out and release # only when the Headset and Speaker buttons are lit again.
5. Enter the following key sequence: 123456789*0#
   The light for the Headset button turns off after you press the 1 key. After you enter the key sequence, the Mute button lights.
6. The phone resets.

Caution: Do not power down the phone until it completes the factory reset process, and the main screen appears.