Yeah, it just needs to be reset. You can try unplugging it, letting it sit for about two minutes, and then plug it back in. do not try to access anything, though, for several minutes. If it's an HD, definitely don't go to those channels. It can take up to an hour to fully restore and going there early can mess it up. If the unplug doesn't help, Comcast can try to reset over the phone. If that doesn't do it, it's a bad box and you'll need to simply trade it in.
A zero usually means the box is not activated.**** Unplug the box for a minute and plug it back in, wait for 15 minutes for everything to reload. If it again says zero contact comcast and check whether the box is activated or not. If it is activated but the box is still not working either you have to get a technician to sort the problem or you have to get a new box.