I had an issue where a client's antivirus program (Symantec EndPoint) was outdated and there was no way to update the virus definitions from the program. The LiveUpdate button was disabled when the program was installed.


For managed Symantec EndPoint Clients, open regedit and navigate to the following entry:

HKEY_LOCAL_MACHINE\SOFTWARE\Symantec\Symantec Endpoint Protection\LiveUpdate\AllowManualLiveUpdate

The value must be 1 to enable the LiveUpdate button on Clients side.