"Due to the new autoplay policies in some browsers, audio and video on the first slide of a course might not work. To fix this problem, Articulate added a play button to Storyline and Studio courses that have audio or video introductions. By clicking the play button, learners give their browsers permission to play the media...Audio and video content on other slides in your course should play as expected. However, if your slides are set to advance automatically without any interaction, media might not work since learners haven't given their browsers permission to play it..."
Storyline and Studio: Media Doesn't Autoplay When Slides Advance Automatically