How to get AirPods Pro 2 hearing aid function to work?

We do not know which settings you have in place, or whether you are using Control Centre to adust or control the hearing feature: You may want to check the set-up, or make setting adjustments:

If you haven't worked through it already, Apple Support's online article (link below) may be helpful:

Use the Hearing Aid feature on your AirPods Pro 2 - Apple Support

Eg: says

"About Noise Control modes with Hearing Aid

The Hearing Aid feature only amplifies sounds in your environment when you’re in Transparency mode. Media Assist makes adjustments to improve the clarity of music, video and calls across all noise control modes."

As well as the linked article about set-up in my previous reply: Apple Support's YouTube video (below) explains how to use the new features, and also explains you can upload audiogram info. obtained from other sources.

https://www.youtube.com/watch?v=Q5noO6dnGBs

How to set up hearing aid function on my new AirPods Pro 2