Okay; did a search for this issue and it did come up, but on the Mac Forum, where it had been erroneously posted.  So first, the problem:

Fin 25/Win10(Anniversary Update.)
 
Fin25 has full functionality EXCEPT when I try to print a part: NO parts show in the printing dialog window.  The files are all (actually) there; it's just that they do NOT show up in the checkmark box, which is completely empty.

I've found contradictory suggestions.  It's been recommended that I immediately INSTALL the Win10 Anniversary Update (which - IS installed - and was, via auto-updating.)  The suggestion (in the Mac Forum) for this precise problem was exactly the opposite: rollback the Win10 Anniversary Update.  But: THAT can only be done within 10 days of the (automatically-installed) update being made.  After 10 days: sorry, you're stuck - have to live with the update.   Of course, I had no idea as it wasn't until well after that update had been installed that I NEEDED to print some parts, and a few more days elapsed before I could identify the cause of the problem: this ^&#(&+"ing Win10 update!

I HAVE discovered a kludgy workaround: I kept Fin 2014.5 installed on this computer and thanks to backwards-compatibility, I open the Fin25 file(s) in Fin2014.5 and all's well; all parts show in the printing dialog window.  But - why should I even bother using Fin25 at ALL now?  There were no direly-needed improvements in the Fin25 upgrade, and now - if it's incompatible with Win10's latest security update, what we have here is an unnecessary program.  

So NOW what?  Anyone, anything to suggest?