Left AirPod not charging

I own an AirPod 2. However, I am having a problem with my left AirPod. There is no sound coming out of the left side. When I double tapped, my right Airpod would go to my previous track but my left one does not get any response. However, if I put my AirPods to their case, the light of the case blinks each time when I put the AirPods inside meaning that the case indicates them. I also tried cleaning the charging contact of the AirPods and the case with cotton buds. My phone says that the left one is fully charged, but it still does not make any noise. Sometimes, the second picture is shown too.

P.S. I could not find AirPods in my devices, so I had no choice to select my iPhone as the problem. Again, I am having issues with my AirPods, not my iPhone.