Hi Patricia,

By default video sound is muted.

To change that you must go to 

/js/jquery.mb.YTPlayer.js

and set mute property to true in player's initialization

More info you can find here:

https://github.com/pupunzi/jquery.mb.YTPlayer/wiki

Thanks

Try jQuery(".player").unmuteYTPVolume(); in document ready, same file

Refer to yt player documentation for more info regarding this method.

Thanks