Play Media when user clicks not working correctly on slide

I have the following slide in my course:

There are object triggers attached to each of the labeled piano keys set to Play Media when User Clicks, and each one links to a corresponding audio file of the correct piano key. When I preview the slide, nothing happens and these keys do not appear to be clickable.

The images of the cow and the bird also have an audio trigger when the user clicks, and these two triggers work fine.

Does anyone have any ideas as to why the other 8 triggers don't work?

Thanks in advance for your assistance.