Go to Settings > Face ID & Passcode > Reset Face ID. When trying to setup Face ID on the iPhone, we get the message 'Face ID is Not Available, try setting up Face ID later.

Start the Camera app and select Portrait in the bottom bar. Switch to the front camera. When the camera detects a person's face, the name of the lighting effect ‘Natural Light’ stays the same. And there is also no flashing red light from the Dot Projector.

Normally, when Portrait mode is ready, the name of the lighting effect ‘Natural Light’ should turn yellow. And there is also flashing red light from the Dot Projector.