Cannot Play Scores in Musescore PC App

The first time I created a score everything worked fine, but when I went to create a score the second time I couldn't play what I had done. The whole playback section is grey/dull and can't be selected at all. I can't bring up the synthesizer either, as it is greyed out too.... I've tried reopening the app with my first score that I had no problems with but it, also, couldn't play.