Endpoint Protection for Mac 12.1 clients display "Client Version Unavailable" in the Endpoint Protection Manager.
Last Updated April 20, 2017
When certain key "SEP for Mac" files are damaged in the Macintosh directory structure, incorrect information is displayed in the Symantec Endpoint Protection Manager (SEPM) console. Though communication with the SEPM will continue, management portions of the SEP client GUI may vanish after the Mac is rebooted. Its GUI will then appear as if it is an unmanaged ("self-managed") installation.
Examining the SymantecRegistry.xml and SymantecRegistry.bak files shows that they have been reduced to 0 bytes.
SEP 12.1 RU4 or older
The size of these files can be seen in /Library/Application Support/Symantec/SMC: