New UPC customers are being allocated IPv6 addresses by default instead of IPv4.
In order to have access to the modem settings for port forwarding you need IPv4. Either phone UPC tomorrow or wait until Monday when someone from UPC will see this and switch you over to IPv4. You then reboot your modem and the settings page will appear.
Having said that … I was under the impression that the entire point of IPv6 was that it allowed every device to be publicly addressable. In other words, port forwarding wasn’t needed; only the port opened and you’d then talk directly from the www to your device on the lan. I’m assuming I’m wrong, as UPC just hand out IPv4 addresses each time someone asks, but I don’t know why I’m wrong 🙂 Anyone know?