Q6 (LGM700DSK) - Face Unlock not working when LCD in off :
Face recognition although has been set to work in screen off mode by default, but user have set
the option to "off" un-knowingly due to which this option may not work in screen off mode.
To rectify the same, plz turn on the setting as explained below
Settings > Display > Lock Screen > Face Recognition
In "Face Recognition" screen, set the "Allow when screen is off" option to ON