I was using Finale 25 for a while, when suddenly the smartsynth sounds became unavailable.  Also with a Mac.  I have many compositions in which most sounds used are Garritan or other, but in one or two cases the built in softsynth sounds are essential and I have always been able to mix them freely.  Now, the sounds simply do not appear despite being present in all menus and appearing to play  back (just not sound comes out.)  This also applies to old files.  It did work at first, and the problem only occurred yesterday in the middle of an important work session.