Hello ntbutcher,
Thank you for using Apple Support Communities.
I understand that you are having issues with the volume on your AirPods. I see that you have already tried a number of troubleshooting steps, resetting, cleaning, checking volume settings, but the issue remains. I would recommend taking a look at this article and make sure you have covered all the bases here.
If your left or right AirPod isn't working - Apple Support
One thing that I have seen from a number of users is that a build up of ear wax in the speakers can cause a lowering of volume. I would recommend double-checking for that also.
If you are still unable to resolve the issue, there is a link at the bottom of that article to contact Apple Support for more direct assistance.
Best regards.