Can't share audio, but only on Audible

My husband has AirPods Pro, and I have Powerbeats pro. We've been able to share audio to listen to an audiobook on the Audible app before. I just upgraded to an iPhone 15 and now we can't share, but only on Audible. I actually can toggle back and forth from a podcast (apple app) to the Audible app and his audio will pick up or drop off depending on whether it's coming from the podcast or Audible. In fact, once I've tried to share in the Audible app, I can't even listen with just my own earbuds, it won't let me click on it. All devices have the latest firmware. How can I fix this?