No issues come up on the HTML5 tracker. My first slide is supposed to play smart object audio before a button. The audio plays in Explorer, but not in Chrome or Edge.
In Edge, the audio is also silent in two other places covering 2-4 slides in 2 different sections. 2 slides don't have buttons, buttons, interactions, or smart shape audio.
You should include a screen capture of your entire Captivate window including the timeline and indicate which object contains the audio. Also, the full version number is helpful when it comes to bugs that have been fixed with newer versions. Without that information, we would only be guessing.
All audio for HTML publishing needs to be loaded on each slide. If you have a lot of audio clips, that may be the cause. Object audio is visible in the tmelines of the object, cannot be paused, not by a button nor by the pausing point of a slide. Object starts playing when the object appears in the timeline. If it is not playing it could be that you have a pausing point before the timeline, or set the On Enter action to Pause and have the object appear later.
You gave the full version number but Adobe itself is no longer supporting version 9, only the two most recent version (10 and 11.5). Are you talking about not playing while Preview or after Publishing?