If the camera stream is missing, it may be because it is still processing. A recording can take up to twice the lecture duration to fully process. The projection stream is typically much smaller and finishes processing first. The recording will then become available. Once the camera stream is done processing, it will attach itself to the recording.
If the camera stream is just a black image, it is likely because you or the instructor before you has selected to block the camera on the touch panel. Please review the How to adjust the Camera Setting article.