How to Factory Reset a Cisco Phone
I made this video because I struggled understanding the instruction from Cisco and I work with this phones on a regular basis.
With the Ethernet cable unplugged, press and hold the # key, insert the Ethernet cable, release the # key after the red light on the headset blink twice then press 123456689*0# on the keypad.
N.B. The first red light on the headset blinks just as soon as the Ethernet cable is inserted.
Good luck 🙂