You were right. installing the OS again made the network work again ! Thank you.
But now, I’m still not able to configure Wifi. As you can see in the following screen capture, the Wifi adapter is not found. When I click Scan, nothing happens.
If it works then you are on the internet. Is that what your asking?
If you have the pi3 there is no need for the WiFi adapter unless you are using cinch. Also you might have to wait a bit for the led light to start blinking in the adapter. That means it is activated.
You could also try following this tutorial by adafruit on setting up WiFi.