ATR,
It appears these are the circumstances of the videos on Youtube: on my pc (windows 7 64-bit) and my apple devices (ipad air 2 and iphone 5), all audio tracks can be heard just fine. Most of us here at my work have Samsungs, so on my note 4, a note 3, and an s5, the narration and audio track linked to video 1 cannot be heard when watching the same link on YouTube. I also tried on an HTC and the same problem exists (perhaps is just an android issue?). Yesterday, I saved the video through Publish+Share and used Premier's built in Youtube uploader to which the same results have existed. You can view that version here: Test Upload - YouTube.
I have now saved a copy of the file, and added the Movie Menu as you described. When I go to "preview disc" and click on "scene selection" and then click on a scene, I hear all of the audio tracks as I expect I should.
Any other suggestions?
Katy