In the SEPM the Virtual Machine Group has the Security Virtual Appliance status as Unknown for some clients but not for others.
Security Virtual Appliance status Unknown for some Virtual Machines
EPSEC driver missing from some virtual clients
Verify this by checking for the driver SymEPSecFlt in Command Prompt
Run > Cmd> fltmc
Without SymEPSecFlt driver installed the client will not see the SVA and give the Unknown error.
From page 672 of SEP install guide.
Symantec™ Endpoint Protection and Symantec Network Access Control 12.1.2 Installation and Administration Guide
The EPSEC 2.0 driver must be installed on all GVMs.
On GVMs hosted by ESX 4.1 with Patch ESX410-201107001 applied,
download the EPSEC driver locally and execute the installer on the
On GVMs hosted by ESXi 5.0 Update 1, do one of the following:
■ Download the EPSEC driver locally and execute the installer on
the virtual machine or
■ Use the VMware Tools installer to install the EPSEC driver.
Note: Perform a custom install and select vShield drivers under
VMware device drivers/VMCI drivers, or perform a complete install.
VMware ESXi Host
Security Virtual Appliance
Shared Insight Cache
SVA per ESXi