Latitude 3550 no wifi connection

Hi 

I've got today the Dell Latitude 3550 and I cannot connet it to the wifi.

I can see my WiFi on the list of the wifi available near me but when  I try to put the password, i got the message of no connection .

It works if I connect the laptop with the cable  to the router and the wifi is working with the other laptop of my flatmates  / or phone.

What can I do? 

Thanks 

Valentina