muteParticipant on lib-jitsi-meet low level API

So I have been following this tutorial handbook and I have successfully set up a conference.

I was looking for a way to mute a participant and I found that in the conference you can do it by calling: jitsiConference.muteParticipant(id); (Note: I made sure as well that id is not null or wrong) but when I tried it, I can still hear the other user. Is this not allowed or is there another way of muting the participant?