After doing everything suggested one AirPod is still muffled

Hello Notarealnameforprivacyreasons,

If you've gone through all the steps outlined in the article you referenced, If your left or right AirPod isn't working, including a full reset of your AirPods, it's time to connect with Apple about service. However, ensure you've fully reset your AirPods first. A reset can resolve many audio quality and power issues. Here's how:

How to reset your AirPods and AirPods Pro

You might need to reset your AirPods if they won't charge, or to fix a different issue.

1. Put your AirPods in their charging case, and close the lid.

2. Wait 30 seconds.

3. Open the lid of your charging case, and put your AirPods in your ears.

4. Go to Settings > Bluetooth. Or go to Settings > [your AirPods].

* If your AirPods appear there as connected, tap the More Info button  next to your AirPods, tap Forget This Device, then tap again to confirm.

* If your AirPods don't appear there, continue to the next step. 

5. Put your AirPods in their charging case, and keep the lid open. 

6. Press and hold the setup button on the back of the case for about 15 seconds, until the status light on the front of the case flashes amber, then white.*

7. Reconnect your AirPods: With your AirPods in their charging case and the lid open, place your AirPods close to your iPhone or iPad. Follow the steps on your device's screen.

How to reset your AirPods and AirPods Pro - Apple Support

AirPods Repair & Service will answer many questions about service options for your AirPods. Note that you may need to adjust the country at the bottom of the page.

Regards.