How to uncover Mute button

I have already set the 'open tikok on mute' button. But don't know why it doesn't work most of the time. I noticed a mute button (a speaker with a x) on the lower right hand corner of the screen which I believe I can mute the video instantly. But the button is covered by a bubble almost immediately. If I touch the bubble, it either does nothing or bring me to a new screen showing Original sound or something at the bottom to select 'use this sound,. How can I ensure that the mute button is not covered.