videoted
I am strictly an Elements Windows user, but I try to seek common ground between Premiere Elements Windows and Mac in certain issues.
Just in case observations....
If you import a video audio clip into the Premiere Elements project, drag it to the Timeline, and mute the audio portion of the clip, you will still get full sound in the Preview Window that you bring up the clip's Preview Window by double clicking the clip's thumbnail in Project Assets.
So, if you have not already, let us explore the audio's volume control at the Timeline level.
a. Running horizontally across the audio portion of the clip is an orange line (rubberband). You can control the audio volume by moving the rubberband up or down. Is the rubberband at the bottom of the audio clip?
b. If you highlight/select the audio clip, go to Adjust Tab/Adjustments Palette/Volume Panel expanded, do you find the volume slider at 0 dB or all the way to the left to infinity?
c. What are the Audio Meters registering when you cannot hear the Timeline clip's sound at the Timeline level?
d. What is the Audio Mixer panels registering for sound volume at the playback of the Timeline clip?
But let us back up a little.
What are the properties of the problematic file in this case - video audio sample or just an audio sample? What are the properties of this file, including file extension?
You say that you worked with 12 before. Was that on Mac with OS X Yosemite?
ATR