Airpod pro Work only single mode

My airpod pro used lated firm ware and my iphone also updated latest ios. Airpod pro doesn't work both side together , only work left or right single mode. checked sound balancing also 50-50. Tried forget device and reconnected. When I place airpod both side in my ear , one side only can hear ear detection sound and work. another side no work. But in setting show both side are connected. I tried to contact apple support live chat but still cannoy settle my problem.