Factory reset your Yealink T46S

• Hold the "OK" button down for 10 seconds or until prompted to initiate factory reset

• Confirm the reset via the softkeys.
• Allow unit to reboot then enter the last 5 digits of the serial number located on the back of the phone. 

• Allow the unit to reboot and factory reset

Once Completed the unit will be reset and will attempt to obtain its new configuration (as long as it is connected to a working connection).