To reset the Wi-Fi of the appliance just keep pushed for 20 seconds the Wi-Fi button on the appliance.
A prolonged beep confirm the reset of the stored Wi-Fi setting After 30 seconds the WiFi icon start flashing fast, that is: 

1 seconds WiFi icon ON 
1 second WiFi icon OFF  

The appliance, then, need to be provisioned again tapping  on overview page.