Why am I not hearing any audio even though it says it's playing?

When you listen to a scanner feed, you're listening to audio that is coming from a real scanner radio that someone in the area is hosting on a 3rd party service like Broadcastify.com.

You can let the person that's providing the audio for that feed know about the problem by going to Broadcastify.com, locating the feed's page, and clicking on the "Report a Problem" button. This will send an e-mail to the provider of the feed letting them know about the problem.