Suspicion confirmed, please take some time to learn to understand the timeline.
Your slide is paused at 1.5secs, due to two interactive objects with pausing points, Previous and Next. Everything what has a timeline starting after that time will not appear until at least one of those objects has been clicked and release of the playhead is allowed by the action triggered by that click.
Since you probably didn't change the behavior of the slide audio by those interactive objects, that audio will continue to play.
I suppose you want to keep those two buttons. Please extend their timeline till the end of the slide (CTRL-E). Move their pausing points to the right until they appear after the last object has entered and/or the last effect has been ended. I can see only part of the timeline, but it should be after 12secs at least.