Fix Face ID Not Working ‘Move iPhone Lower Version’ Issue

Fix Face ID Not Working 'Move iPhone Lower Version' Issue
Fix Face ID Not Working 'Move iPhone Lower Version' Issue

Make sure the TrueDepth camera isn’t obscured by anything. Remove any obstructions to the TrueDepth camera, such as dirt, a case, or a screen protector.

Make sure your finger or palm isn’t obscuring the TrueDepth camera if you’re using an iPad in landscape mode. If it is, an alert with the words “Camera covered” and an arrow pointing at the TrueDepth camera may display at the top of the screen.

Make Sure Your Face Isn’t Hidden: If your face is obscured by something, Face ID won’t be able to detect it. You must ensure that the camera can see your mouth, nose, and eyes. Face ID usually works with glasses on, but if you’re getting the Face ID not functioning message with them on, try it without them.
What exactly is the function of the Flood Illuminator?
To illuminate the user’s, the Flood Illuminator emits infrared (IR) light. 
Infrared (IR) light is wavelength of light that is invisible to the naked eye and is part of the 
electromagnetic spectrum.
Can dropping your phone make Face ID stop working?
Unfortunately, FaceID technology is built on a multitude of sensors that are quite weak and will easily break if the phone is dropped (particularly the dot projector), which is why humidity and minor bumps frequently result in faceid being permanently destroyed.