Rush CC on Win 10. Preview has sound; Export to MP4 in stereo has no sound

So, I selected the defaults for the first Export.  Stereo, etc.  I exported to my local machine. 

The MP4 vid looks fine.... however, there is no sound.

I tried other MP4's on my computer, and the sound is fine. 

Tried the second test.Again, there is sound (of me talking) in the Preview.

I export to the local machine with Mono as the selection.

I have success in Mono.