Can't hear music I composed

Hi, my name's Pamela. I've recently just started using Musescore to write my compositions and little ideas in. It was working perfectly fine on the first day and today is my second day using it. I'm still trying to get used to it, but whenever I try to listen to what I have scored out, it wont play. The play button is not optional and I don't know what to do. More accurately, I don't know if I pressed anything that has something to do with the play button not being optional. Thanks