If you are using iOS mobile phone to watch, there are two different audio systems in iOS, one for system (like telephone ringing) and one for apps (music, videos, etc.). Sometimes you can only change the one for system but not the one for apps. It’s suggested to restart your phone and try again. If it still doesn’t work, please send us the name of the video and the name of your mobile phone and its version.
If you are using the web or Android mobile phone to watch, please directly send us the video name, the name of your browser/phone and system version.