Sound loss on one side

If you can hear through it the sound duct is clogged with junk! Just dampen a Cotton Q-Tip with some isopropyl alcohol (not wet!) and carefully clean in stages the duct port, you should not need to enter, if you do you do risk pushing the junk into the sound chamber.

Here's a guide someone wrote up AirPods 3 정밀 세척 방법 (이어버드 전용) scraping off the big stuff makes sense. Mine don't have any screen unlike these.

The single-side quietness on AirPods 3 almost always comes down to one of three things: (1) the sound duct/mesh on the quiet bud is clogged with earwax or dust — the cleaning answer above is the right first step; (2) the balance slider got bumped — check Settings > Accessibility > Audio/Visual and make sure Balance is centered; (3) a degraded ear-tip seal. Quick test: swap the tips between buds — if the quietness moves with the tip, it's fit, not the driver. If cleaning plus balance doesn't bring the left side back, these AirPods quiet fixes (https://fixmyphonespeaker.com/blog/why-a...) walk through the remaining checks (mono test tracks, reset procedure, when it's actually a dead driver). (Disclosure: I help build FixMyPhoneSpeaker.)