You can troubleshoot in the following ways:

1. Check the internet connection of your home Wi-Fi.

2. Ensure that your home Wi-Fi password has not been changed.

3. Avoid using a metal faceplate on the wall switch, as it may reduce the Wi-Fi signal.

4. For the US version of the switch, please restart the switch by pressing the restart button(refer to the photo below).

If all other methods fail, press and hold the power button for 5 seconds to restore factory settings, and then try to add the device again.