CAMERA  COVER

If you have a Dell Model - Latitude 7400 and your camera does not show anything, or shows black, it could be the camera's privacy cover/slider is in the closed (red dot showing) position.

Please confirm that the camera's privacy cover/slider is in the open (no red dot) position, before using video communication.

Also See:
Latitude 7400: Visual Guide to your computer
https://www.dell.com/support/article/en-us/sln317020/latitude-7400-visual-guide-to-your-computer?lang=en