Use the following process to download the system's current identity certificate. The certificate file can then be renamed and uploaded to the file server being used by the IP Phones.
Browse to the IP Office system IP address and select IP Office Web Manager. For example, IP address: https://<server_address>
Login with an administrator account.
Click on Solution.
Click on the icon next to the system and select Platform View.
Select SettingsGeneral.
Scroll down to the Certificates section.
ADDITIONAL INFORMATION:
Click Download (PEM-encoded) to download the system's certificate file.
Rename the file as WebRootCA.pem. This is the default name set in the settings file using the TRUSTCERTS parameter.
Upload the file to the file server 40 being used by the phones.