WiFi is not working

Because you tapped the Wi-Fi icon in Control Center. 

So the Wi-Fi icon turn to 'white' -> Wi-Fi Is deactivated.

To activate the Wi-Fi again, it will be turn on to 'blue' again.

And you will have Wi-Fi connection again.

To turn Wi-Fi Off or On, go to -> Settings -> Wi-Fi.

But why you turn Off the Wi-Fi network?