If the power falls and Sonoff is connected, when the power returns, Sonoof remains disconnected.
what could I do so that Sonoff remains conected?
Look in the Device Setting menu and set the power on state to ON
Your Sonoff should automatically reconnect to wifi when the power is restored. You also can set the power on state of the relay in the ewelink app as ON, OFF, or KEEP. Keep will resume the On or Off state the device was in when the power failed.
I don't have acsess to set it up in firmware 2.02