This Course will give you a few tips about managing features on your Cisco Phone:
Go to the settings page of the phone
Press *,*,#,*,* (star, star, pound, star, star) about 1/2 second apart
The phone will display “Resetting” and perform a hard reset
This sequence will cause the phone to reboot as if the power cable had been unplugged and force it to pull a new configuration from CUCM. Once common issue I find when entering this code is the keypresses not registering with the phone. Try it a couple of times until you develop a rhythm for entering it about 1/2 second apart. Much more than that and the phone won’t think you’re entering the code. Quicker than that and the keys might not all register.