I'm trying to figure out why my Android smartphone isn't showing notification on the lock screen when I receive a new Skype message. After some researchings, I found that it seems to have something to do with a featured called "Ambient display".
As this article explains, Ambient display is a feature introduced on Lollipop (Android 5.0) and above, and it wakes the device and light up the display for a few seconds when new notifications arrive.
My Android version is Nougat (Android 7.0) so it is supposed to have Ambient display. But after I followed the instruction of that article and went to Setting > Display, I cannot find any option called Ambient display.
Why doesn't my Android 7.0 smartphone have Ambient display?
== Edit ==
My device is CAT S41.