I am not an expert with Photoshop 3D, but try selecting something other than the Move tool to make the ground plane etc. disappear. Now this may not be the right way to do it, but if you copy the 3D layer and rasterize the copy, you can save that as a JPG, or turn off the background layer, and save a PNG with transparency. We'll see if our davescm can give you a proper answer.
After rendering, then the rendered layer should stay unless you change anything in it. The slightest movement and you will be back to an un-rendered version.
However , you may be misled if you have the move tool selected. With that tool, the groundplane grid will re-appear as an overlay on the rendered version. Change to another tool and it will vanish.
When you say you have "activated the groundplane" can you describe exactly what you have done. Unless you put something solid there (e.g. a flat object) the groundplane is transparent although the panel settings will create shadows and reflections on that transparency.
These tutorials should help you, they refer to CS6 but most things remain unchanged up to 2017.1 apart from constraints which appear to have been partially removed :
Thank you all for your feedback. What you suggest seems to be what I have discovered. I am just accustomed to 3D programs that create a non-volatile render, meaning that render is not part of the build space and does not go away based on anything you do in the build space. I guess I was expecting the render to appear on it's own layer and not be so "delicate" that you could destroy it so easily.
As to the ground plane, I now realize that it does not render as a plane but as an invisible surface that catches shadows.
Regarding the documentation, I have looked at that first and discovered that CC 2017 is very different than the documentation available online for CS6. There are missing dialogs and buttons that are referred to in the current docs. Even the offshore chat help said the docs are not updated for the current versions.
Again, thanks all!