Looks like I found at least one cause of the camera going black. Moments ago, I stumbled on the simple reason why my Litchi flight plans, written in the Litchi Mission Hub on my desktop computer, weren't showing up on my iPad's Litchi screen, namely that I didn't log in. My elation over discovering this very small procedural error, quickly became my undoing.
In my excitement to try my first ever Litchi waypoint mission, I forgot to remove the camera lens cap, before starting up the drone. The lens cap was protruding a bit, since it wasn't pressed fully down on the camera, so when I started the drone, the camera lens was in contact with the table I use as a landing platform, thus preventing the camera from swiveling about freely, as it does with each startup of the drone. Subsequent startups of the drone did however show the camera swiveling about normally.
I normally don't affix cap fully down to cover the entire camera because it does take considerable force to press it fully down, which I had been avoiding out of concerns that doing so might damage the gimbal while installing or removing the lens cap. I now profoundly regret that practice of lightly affixing the camera lens cap, because it is possible such a simple oversight, has in essence cost me the entire drone, since it remains disconnected in both DJI Go and Litchi platforms.
As a footnote, I did try re-linking the drone to the controller using the link button, gimbal rotate to the left, and S2 switch toggling process described on page 24 of the Phantom 2S manual, and the link button did glow solid green to confirm a link was established. Despite that small victory, the drone remains disconnected from both DJI Go and Litchi, while the camera image remains flat black. To describe my current mood as dejected, would be a major understatement. The design of the Phantom3S camera lens cover, is a booby-trap waiting to destroy the drone, after one single and brief lapse in concentration.