The IP address or network you're using has been blocked. Most often this happens while using a VPN or proxy, especially if the service has been abused by other people. It's also possible that your ISP has been identified as a safe haven for abuse, meaning that it doesn't attempt to stop unlawful activities on its network once they're reported.
If you're using a VPN, note that while we appreciate the need for privacy, Sickgen is a place where there are no interactions with others users so, you can be quite. Using a VPN makes it more difficult for us to identify spammers before they have a chance to do something, so we'd appreciate if you disabled while using the site. We generally block networks once they become sources of abouse; since many people use public VPNs, they often end up blocked. We try to only block new registrations, but sometimes more aggressive restrictions, like the one you've encountered, are necessary.