Audio on Layers not playing when clicked again

What you're describing sounds like the intended functionality of Storyline. 

When you click on a button to show the layer, even though that button exists on the base layer, the button itself can be visible on a layer, but its trigger lives on the base layer.

For example, if I have four buttons on my base layer that show Layer 1, Layer 2, Layer 3, and Layer 4. When I click on button 1, I am navigating AWAY from the base layer and I'm now on Layer 1. Clicking the button again will not restart the timeline of layer 1, which is what it sounds like you are hoping it would do.

One option would be to copy and paste the button from the base layer onto layer 1, and create a trigger for it on layer 1 that jumps to time 0m 0s.

Here's a Peek video explaining!: https://360.articulate.com/review/content/65cb1cbc-ebbf-411c-bb4c-725d86ddc33d/review