User x-crafts seems to have the answer to this:
If the WORLD is "hidden," but your geometry group is visible, you don't get geometry in an export.
If you make the WORLD (everything) visible, select your group and "hide unselected," the WORLD "eye" still shows and on export, you get geometry in your output file.
This is a good workaround. I would think, though, that if any individual group is active, then the WORLD "eye" would be visible by default. That's just my sense of things.... but if I've got a reliable fix to save time saving and then reloading what can be pretty big files, that's huge!
THANKS, X-CRAFTS!!!