This means that the front camera of your iPhone seems to be that it is not working
Try this
- Remove any case, accessory, or film that might block the camera or flash or that places a magnet near the camera.
- Test the camera by trying to take a photo.
- Test the LED flash:
- Try the flashlight in Control Center on your iPhone or Control Center on your iPad. On an iPhone X or later or an iPad, swipe down from the upper-right corner of the screen. On an iPhone 8 or earlier, swipe up from the bottom edge of any screen.
- Tap the Flashlight button.
If the flash works only sometimes, open the Camera app and tap the flash button to choose a different setting.
A configuration profile, including a Mobile Device Management (MDM) profile, can disable the camera.
If the camera or flash still isn't working properly, contact Apple Support to discuss service options.
See this link for further reference
If the camera or flash on your iPhone, iPad, or iPod touch isn't working - Apple Support