Logging in AirOS router from other network

Me and my friend are playing, he gave me his IP address and with that, when I put his IP in my browser I get his router’s log in page. He is using Ubiquiti airOS and on internet I saw that the default for username and password is: ubnt. But it doesn’t work; I tried several other passwords but still nothing. I wonder why is that happening? I don’t think that he changed the password or something like that, maybe a firewall is blocking it because of “outside” log in? I am beginner so please detail explanations. Thank you!