To perform a factory reset on your Sonos speaker, follow these steps:
1. Unplug the speaker from the power source.
2. Press and hold the Join button (or Play/Pause button on older models) located on the speaker.
3. While holding the button, plug the speaker back into the power source.
4. Continue holding the button until the status light on the speaker flashes orange and white.
5. Release the button.
6. When the status light flashes green, the factory reset is complete.