Bonjour,
les matériels installés après la mise restent hors ligne. Quelle est la solution ?
Merci
This forum is 99% primarily English-speaking. If you expect the greatest possible reach of your post, it is worth writing in English, even in broken English, but in English.
By not communicating in English, you give the tone of your post as privileged and arrogant, not bothering to write in English and transfer it to another person to translate from your native language into English and then expect them to help you…
You didn’t even write what device you’re talking about, so I’m guessing from your post from another thread that it’s probably DW2…
In the future, make a little more effort in communicating with people. 
In the case of DW2-WiFi, insert the batteries, press and hold the button in this small hole for at least 15 seconds, after which you should see a blinking red diode.
Now you can perform pairing in the ewelink app.
DW2 needs access to the cloud to work, make sure it has an unblocked connection to the Internet via TCP 443, 80, 8080…
Determine whether the problem is with access to the cloud or connection to your Wi-Fi network, or whether the device does not work at all… perhaps it is damaged.