How to fix AirPods 4 ANC not working on iPhone?

I’m really perplexed—my AirPods 4 Active Noise Cancellation (ANC) isn’t working at all. I’ve tried everything: restarting, checking settings, updating firmware, resetting the AirPods, etc., but nothing fixes it.

Has anyone else had this happen or figured out a solution? Could this be a hardware issue? Any insights would be greatly appreciated!