well, this may be a little late but I had a similar problem on my right side AirPods (AirPods Pro 1Gen). In my case, in addition to not being charged, they do not disconnect from my phone when I put them in the case and close the cover (I guess it disconnects when it detects it is being charged). I literally hear the sound playing inside the case.
Anyways what I did was I Chewed on the tip of a toothpick to make it soft and look like a little brush. Then I used that to clean the metal part inside the case with as little force as possible. I also wipe the metal parts on the AirPod itself and voila, now it is charging properly and disconnects when I close the cover.
I do this regularly now because dirt is a part of our lives 😉
Hope this helps. Cheers!