Music not sounding

I downloaded the new update for musescore two days ago and been using. Starting two days ago, when ever i want to hear what I've composed, it won't play any of the notes. It will highlight the notes like it was playing but will not play the audio. I want to know if you could help me with that? Also the sound button in the mixer window isn't allowing me to choose anything or have thing on it. Also, I'm using Musescore 2 on a mac pro.