Audio doesn’t work correctly in student preview

[NohaElba]

Hi all, I recently published my language course; I checked the audio and video of it and everything is fine.
The strange thing is if someone wants to watch the presentation video or the free lessons, he can hear the background music only without hearing me talking. 

When I tried to view the  course as an instructor, I could hear everything. 
so what’s the problem?? 

[PhillipBurton]

Did you record your audio track as mono?

It may need mixing as stereo.

Phillip

[NohaElba]

camtasia audio set

vid audio video properties

These are the video settings.