If you upgrade an Expressway server and do not check if the server certificate has expired, you may have to restore the default certificate via root access.
Remove the following files via root access:
If this is not possible for some reason you can also perform a factory reset and preserve some settings (Option Keys, etc.) – You will loose the “Release Key and the Expressway will be a “Cisco TelePresence Video Communication Server Control” after Factory Reset.
Reference Web Interface:
Recover Expressway Web Interface
Reference Factory Reset:
Restoring the Default Configuration (Factory Reset)