Why would Blu-ray made with Encore CS6 be silent/have missing audio, no sound? Any thoughts on why audio might be missing from such a project?

Steps:

1) 3 mkv files 1280x720 25P, stereo audio (2 channels)

2) converted to mp4 using ffmpeg

3) audio still present

4) created premiere pro cs6 hdv project

5) lines up the 3 files, back to back

6) confirmed audio still present by listening in the monitor

7) saved project

8) created encore cs6 project, H264 blu-ray, 1280x720 50 (25 not selectable)

9) confirm audio still present in monitor

10) create blu-ray image

11) burn it with imgburn

12) watch blu-ray on vlc player - no audio

13) on MPC-HC player - no audio

14) on cyberlink powerdvd - no audio

I've just started to repeat the steps, this time in step 8, selecting PCM audio instead of dolby (in first attempt), as the original signal is 2 channel.

Playback through Yamaha SW1000XG sound card, stereo out on Windows 8 desktop.

Encore blu-ray generation done on Mac. blu-ray image burnt using imgburn on windows 8 desktop.
The only thing I can think of is that the audio channel may not be getting set on the timeline for some reason.  I would verify what audio track is associated by default with the timeline as a first step and try a simple case of a disk that immediately plays the timeline with the audio set to the default audio track.  If that still doesn't work, I'm out of ideas.  Your situation seems very odd.  Have you tried playing it in a stand alone bluray player by any chance?