When your IP 331 device has been reset but the phone did not download the configuration file (IP Soundpoint will be displayed on the phone instead of the extension number), you have to manually enable ZTP on the phone.
1. Press the Menu button and choose Settings in the options
2. Select Advanced
3. You will then be asked to enter password. Please enter 456 (or 3636 if that does not work) and then select OK.
4. Next, select Admin Settings
5. Next, select Network Configuration
6. Select Provisioning Server:
7. Press the down arrow key until you find ZTP
8. Select ZTP by pressing the middle button and press the left or right arrow to enable ZTP.
9. Press the Menu button to go back to the home page which will prompt you to save the config. Select Yes.
The phone should now reboot and the config file should start downloading shortly.