I have the same problem. Installed this mornig a new Shelly DUO, it has been online for a few minutes, but suddenly went offline. It came back for a few minutes, but since then, nothing. I've been pinging it for more than an hour now, nothing.
I don't understand why. Wifi signal is very good here. Latest firmware.
Anyone any ideas?
Will send it back if it doesn't get resolved.