No opensky name in the receiver

Hi everyone, I have bought an ADSB reciver in order to collect and provide data. The problem is that when I follow the instructions of the website and I arrive to the step of "Determining the IP Address of Your Receiver", when I tip "nslookup opensky" in the command shell, the name of the server that appearsis SERVER and not OPENSKY.
So the addres achieved don't allow me to see the results of my antenna.
PS: I add photos of my result and the explanation one.
PLEASE HELP !!!!!!!!!!