Here are some potentially relevant log events that were generated when I attempted to download LiveUpdate content:
Symantec Endpoint Protection Manager,06/29/2017,10:50:15 AM,SEPM,7210,Information,Classic,Content,N/A,<hostname>,IP:<ip_addr>,7210,Scheduled LiveUpdate session started.
System,06/29/2017,10:50:17 AM,Microsoft-Windows-DistributedCOM,10005,Error,Classic,None,N/A,<hostname>,IP:<ip_addr>,10005,DCOM got error "14001" attempting to start the service LiveUpdate with arguments "" in order to run the server: {03E0E6C2-363B-11D3-B536-00902771A435}
System,06/29/2017,10:50:17 AM,Service Control Manager,7000,Error,Classic,None,N/A,<hostname>,IP:<ip_addr>,7000,The LiveUpdate service failed to start due to the following error: The application has failed to start because its side-by-side configuration is incorrect. Please see the application event log or use the command-line sxstrace.exe tool for more detail.
Application,06/29/2017,10:50:17 AM,SideBySide,80,Error,Classic,None,N/A,<hostname>,IP:<ip_addr>,80,Activation context generation failed for "C:\PROGRA~2\Symantec\LIVEUP~1\LUCOMS~1.EXE".Error in manifest or policy file "" on line . A component version required by the application conflicts with another component version already active. Conflicting components are:. Component 1: C:\PROGRA~2\Symantec\LIVEUP~1\Microsoft.VC90.CRT.MANIFEST. Component 2: C:\PROGRA~2\Symantec\LIVEUP~1\Microsoft.VC90.CRT.MANIFEST.
Symantec Endpoint Protection Manager,06/29/2017,10:50:18 AM,SEPM,7201,Warning,Classic,Content,N/A,<hostname>,IP:<ip_addr>,7201,Content download to the server failed.
Symantec Endpoint Protection Manager,06/29/2017,10:50:18 AM,SEPM,7211,Information,Classic,Content,N/A,<hostname>,IP:<ip_addr>,7211,LiveUpdate session completed. Total time elapsed: 2 seconds.