How to Factory Reset or Reboot AirPods?

See the AirPods User Guide:

Unpair, restart, or reset your AirPods - Apple Support

Return AirPods to factory settings

If your AirPods aren’t working correctly after you restart them, you can return them to their factory settings. 

Do one of the following:

• AirPods (all generations) or AirPods Pro (all generations): Put the AirPods in their case, close the lid, then wait 30 seconds. Open the lid, then press and hold the setup button on the back of the case for about 15 seconds, until the status light flashes amber, then white.
• AirPods Max: On the right headphone, press and hold the Digital Crown and the noise control button at the same time until the status light next to the charging port changes from flashing amber to flashing white (around 15 seconds).

The same instructions are in a different document with listed steps:

How to reset your AirPods and AirPods Pro - Apple Support