LUbuntu light-locker-settings didn't start (cannot activate screen dim)

Lubuntu based on Ubuntu 16.04LTS
When I click on Light locker settings it does not show the menu for light-locker and worse I noticed that my screen does not dim at all

In order to make Screen dim work I installed xscreensaver but did not work either: When i clicked on the screensaver icon in /usr/share/applications it said the following:

The XScreenSaver daemon doesn't seem to be running on ":0". Launch it now?

In order to launch it automatically  I added xscreensaver -nosplash   in
Preferences -> Default Applications for LXSession -> Autostart

Now it is automatically started and after I adjusted the timings for the screensaver it works as intended.