Nikon d800 light assistant beam not working?

The light assistant works only when the camera chooses the focus point in single mode shooting. When turned on one point the light beam doesn't work, any ideas on how to make it work all the time in more focusing modes than just that one?

As I understand it, it only works in the dark. I may be wrong though. Time to read the manual.

It will only work in one shot as the other modes have your focus constantly changing so it would destroy the camera's battery by keeping the light on and would interfere with your photos.
Check the custom functions in your menu, there could potentially be an option to change the setting but it's highly unlikely.

Consult your manual if you have further issues.