When viewing just my camera in fullscreen, I can see video. But when I try to view multiple cameras in, say, a 4x4 view, my camera is suddenly not appearing. Why is this?
When viewing a camera in fullscreen it is outputting the Main Stream, when viewing in multiple views it is by default outputting the Sub Stream. If the Sub Stream is not appearing, first you must verify that the camera has a Sub Stream to output in the first place. Cameras with multiple lenses will typically not have Sub Streams. If you have a standard camera that you are sure should be outputting a Sub Stream, you will likely need to default that camera. To do so, log directly into that camera's web interface and navigate to Configuration -> Maintenance and select the Default option.