I’m missing something in your post then.
Are you asking exactly what the mechanism for getting a direct video stream from a camera is? Depends on your camera, but it’s almost always RTSP.
Are you sure your camera even supports streaming off camera? You can try opening an RTSP stream from the camera with VLC as a quick and simple test to find out.
Then you need to go looking in your logs. You mentioned nginx, so go check those logs, or the WordPress logs and see if you can get any info. Wouldn’t hurt to also check your browser console output and see if there are any errors there when attempting to load the page.