Tutorial on iPad lost sound


Wondering I’ve a strange problem with the tutorial on my iPad. It worked perfectly fine on first time after installation. Then I tried to continue the tutorial after sometime apparently the video is playing just fine with subtitle but no voice comes out from the video while it is playing, tried minimize and maximize the window still same, restarted my iPad and reinstalled the app but to no avail still no sound comes out. Is there a mute button inside the app to turn that off? It is pain to look view the tutorial on my iPhone and practice same but on iPad…

Many thanks in advance.