Slideshow Module on Lightroom CC Not Working

I am a longtime Lightroom user, but am trying to use the Slideshow module for the first time.  I have my photos and my music selected, and am using the "Simple" Lightroom tempate, with music synchronization.  When I try to preview what I have, I can hear the music and I can see it "progressing" through the images down below in the filmstrip, but the slideshow is blank -- I can't see any of the images.  Any thoughts as to what I might be doing wrong, or what might be wrong with the program?  Thanks!