my youtube video not playing sound on android phones

Hi, anybody knows why my youtube videos are not playing sound on android devices?
Here's the video link:


This other random below video, on youtube, it plays well on android devices.


I'm guessing there is some issue either with my chael or with my video which I made using ffmpeg
Could someone please tell me what's going on? Some ffmpeg tag I need to include while encoding the video?
Thanks