You need to disconnect the router (or Wifi Access Point) that it's connected to.
Then wait 30 seconds
Then It should show up again as wifi AP that you can connect to.
THEN YOU need to connect to it and Plug in and turn on the router (or Wifi Access Point) that the board was originally connected to.
By now you should be able to see the configuration panel of the Arduino Uno Wifi Developers Board.
I hope this helps!