You need to update Symantec Endpoint Protection Small Business Edition (cloud) agents manually using a script or a schedule.
This document apply to SEP SBE installed on Windows Workstations Operating System.
The command to execute to launch Liveupdate for Small Business Edition is as follow:
"C:\Program Files\Symantec.cloud\EndpointProtectionAgent\Engine64\<version>\uistub" /lu
"C:\Program Files\Symantec.cloud\EndpointProtectionAgent\Engine64\18.104.22.168\uistub" /lu
However, as there is no switch available to launch the command silently, end-users will need to click the "OK" button once the update ends.