Sometimes it may be necessary to reset the Apple HomePod Speaker to factory defaults, i.e. the state it was in when it was shipped.
This is usually the case when the device can no longer be controlled via the app.
The following step-by-step instructions describe the factory reset procedure:
Performing an Apple HomePod factory reset
The Apple HomePod is reset by pressing on the top. This is usually done when the device can no longer be controlled via the app.
1. Disconnect the Apple HomePod from the power supply by unplugging the power plug.
2. Wait about six seconds and then reconnect the device to the power supply.
3. Wait approx. 6 seconds again
4. Now touch the top of the Apple HomePod with your finger and hold the top until the white rotating light of the HomePod turns red.
5. Keep your finger on the top of the device.
6 Siri will now tell you that the Apple HomePod will reset to factory defaults.
7. If you hear three consecutive tones, you can take your finger off the Apple HomePod.
You have now successfully reset the Apple HomePod to factory defaults and it can be set up again.