It wouldn't surprise me that Twitter would block his IP from making new accounts. (Each Internet connection is associated with an IP address.) I will give him the benefit of the doubt and say that he couldn't sign up with a VPN/Tor and he's been IP banned from making new twitter accounts, and he has an IP that he doesn't know how to change, so he has to connect to a network with a new IP to register a Twitter account.
Of course, I don't know how Twitter does bans, but I assume you can't just keep on signing up for accounts after you've been banned from your 20th.