Make sure your phone has power and is connected to the Internet. Press the Setup button.
Navigate to Menu Item 14 – Factory Reset and press Select. It may request a password. Enter 456789 then press ok. It will take you back to the setup menu. Press Factory reset once again, then press ok.
Press OK at the Reset Warning => Commencing Reset
You will see a blank screen during the initialization process. There will be blinking lights followed by a Cisco logo:
Initializing Network will appear on the screen
Once phone has fully booted, the phone will have been factory reset and the following image will appear on the SPA504G screen.
If you're a customer on a managed network, Gazelle will have set up your phone to automatically provision. Wait approximately 60 seconds, and then the phone should reset & go through a configuration process. Once complete, all 4 line buttons will be lit up green, and the extension information will be displayed on screen.