Monitoring the CSS tunnels is crucial to the environment to know if it's working as intended and that all is up and running.
Environment configured with Cloud Secure Services (CSS).
Monitoring your CSS tunnels on your VCO.
-From the VCO you can go to monitor--->Cloud Security Services--->Cloud Security Services Sites, this should give you an overview of the configured CSS tunnels in your environment and their status.
-Furthermore on the monitor tab of the edge, you can allow edge tunnels in the view to see the status of each tunnel connected to your edges.