AirPods Pro transparency mode not working

As the topic, the transparency mode of my AirPods is not working since last Wednesday, which was the day I realize the problem. When I was switching modes by clicking and holding my AirPods, I can hear the mode change and the click sound, but it didn’t make the sound go clearer, and the only thing changed is the slight buzzing sound in transparency mode. Simply, the transparency mode has the almost the same function as the noise canceling mode and lost its original function that is supposed to work. I tried to reconnect, reset, and putting my AirPods in and out of the case for multiple times, and it still doesn’t work. I don’t think it relates to the iOS system, cuz I tried it with my iPhone, iPad and Mac, all of them didn’t work. Besides, my iPhone has the newest iOS system. I don’t think it relates to physical damage either, cuz I’ve used it for almost half a year and I barely damaged it.