The ProxySG or Advanced Secure Gateway appliance health is in a Warning state due to Health Check Status. The appliance health checks (Statistics > Health Checks) show that iso.server is unhealthy, as follows:
Symantec Web Isolation was released in version 7.3.x, with the ability to configure dedicated web isolation servers. The Symantec cloud Web Isolation service, for which the health check is created by default, is available with the release of version 7.3.4. This should be resolved now that the cloud Web Isolation service is available.
To work around the issue, set the iso.server health check to Disabled: Healthy.
Note: If you plan to use Symantec cloud Web Isolation service later, change the health check to Enabled.