You can troubleshoot in the following ways:
- Check the Internet connection of the home Wi-Fi.
- Make sure your home Wi-Fi password has not been changed.
- Do not use a metal faceplate on the wall switch, as that will reduce the Wi-Fi signal.
- Restart the switch by pressing the restart button.
- If all other methods fail, press and hold the power button for 5 seconds to restore factory settings, and then try to add again.