FYI, if anyone is having the same problem, I have found the
solution. I had the Single Source Layout "pod" hidden (RoboHelp 7).
Once going through the View menu to display it, simply
right-clicking on the primary layout, selecting properties, and
specifying the default topic did the trick.
The silly thing is it was already specified in that
area....apparently re-specifying it "woke it up."