After upgrading to 2.4.9.1 from a lower ISG OS version - on the Management center there can be a warning in SSP Health Check: "Appliance Certificate Validation Status as Error"
Under health-monitoring view events it shows Appliance Certificate Validation Status : Unknown.
In 2.4.9.1, this health monitoring parameter (Appliance Certificate Validation Status) was introduced and it takes around 24 hrs for the next certificate check to get triggered and status changing to OK
This is documented as 'ISG-1857 Health monitoring now includes a metric for birth certificates, so that a warning is issued when a certificate nears expiration' in the release notes
Resolution:
1. SSH into SSP
2. enable
3. #configure terminal
4. (config)# ssl
5. (config-ssl)# view keyring bluecoat-appliance
6. After next certificate check (it check every 24hrs) system should show valid certificate.