The PVO cannot be enabled and shows this type of error message.

Unable to proceed with Centralized Policy, Virus and Outbreak Quarantines

configuration as host1 and host2 in Cluster have content filters / DLP actions

available at a level different from the cluster Level.

The error message can indicate that one of the hosts does not have a DLP feature key applied and DLP is disabled. The solution is to add the missing feature key and apply DLP settings identical as on the host that has the feature key applied. This feature key inconsistency might have the same effect with Outbreak Filters, Sophos Antivirus, and other feature keys.

https://www.cisco.com/c/en/us/support/docs/security/email-security-appliance/118026-technote-esa-00.html