I've been using PP for the past 18 months and never had this issue.
I have an AVCHD file that I have mutilple clips in. When I place them into the SEQ and then attempt to listen to audio 2 or 3 I don't hear anything, and yet if I UNMUTE audio 1 I do hear it?
I know this has to be obvious. Here is a screen shot. You can see that A1 is muted and A2 and A3 are playing, yet I hear nothing. If I unmute A1 I do hear it (and only it).
You've got a 5.1 Master in your sequence, with tracks 2 and 3 sent to the surrounds, center and sub. My guess is you only have a stereo speaker setup, so anything not sent to left to right has no corresponding speaker to produce the sound.
Create a new sequence with the proper Stereo master and copy/paste all your clips into that.
Ok, all three clips are just 2 track Stereo. What do I have wrong in my settings that I'm not able to audition each track in this seq?
See post 1.