First, make sure your relay is plugged into a mains socket.
Have you changed the Wi-Fi password of your Wi-Fi router or installed a Wi-Fi repeater? If so, you must reconfigure the network for your relay in the Netatmo Energy application.
For more information concerning connectivity problems with your Netatmo products, please look up Netatmo Support at (add the following hypertext link: https://www.netatmo.com/fr-FR/helpcenter/energie/3/mon-relais-est-injoignable-que-dois-je-faire/79 )