You say you've done this:
- Click on this link to learn 'How to clean your AirPods, AirPods Pro, AirPods Max, and EarPods' --> https://support.apple.com/HT208729
In general make sure there is nothing blocking or stuck in the tip.
Make sure it isn't a setting thing:
- Customize headphone audio levels on your iPhone or iPad --> https://support.apple.com/HT211218#manually-adjust
Check the audio level balance. Go to Settings > Accessibility > Audio & Visual > Balance
(On older systems: Settings > General > Accessibility)
After that:
- Contact Apple Support about AirPods sound issues by clicking here --> https://getsupport.apple.com/?caller=kbase&PGF=PGF32003&category_id=SC0285&symptom_id=23222