Left AirPod not working and won't connect after reset

Which AirPods do you use?

Are both AirPods charged?

Charge your AirPods - Apple Support

Any error messages if you want to pair the AirPods?

Pair AirPods with an Apple device - Apple Support

"Left AirPod not working and won't connect after reset: Yesterday, I tried connecting my AirPods. When I used them, only the right one worked while the left one didn’t function at all.[...]"

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They both need to be inserted to work. So, it's likely debris.

Troubleshooting AirPods Connectivity:

A Few Thoughts to Try:

A. Start by wiggling it in your ear.

B. Charge these to 100%

C. Visit Apple Support links:

• If your AirPods Won't Connect – Apple Support
• Connect and Use your AirPods and AirPods Pro – Apple Support
• If you can't Connect a Bluetooth Accessory to your iPhone, iPad, or iPod touch - Apple Support

D. Verify the Balance:

1. Go to: Settings
2. Tap: General
3. Tap: Accessibility
4. Scroll Down: to Hearing
5. Adjust: the audio volume balance

E. Clear Out Earwax:

Go Here: How to Clean your AirPods and EarPods - Apple Support