EOS 5D Mark IV: Face Detection AF in Live View

Face Detection AF makes it easier to find and follow a person moving around the frame. The camera will identify the face and then keep it in focus as your subject moves. If you find the camera is not detecting the face, ensure it is towards the middle of the frame – at the edge of the frame the camera may be unable to identify a face. By starting with the subject near the middle of the frame, the camera has the best chance of identifying the face and then tracking it out to the edge of the frame. Also, if the subject is very out of focus, you should manually focus closer to the required focus distance so the camera can identify the face more accurately.
Camera settings
EOS 5D Mark IV