3.1.1 error

Though the reps will need to make the ultimate determination as to what's going on, I'd check to make sure that the coax connector is at least finger tight at the back of the modem. It doesn't need to be tighter than that, but it shouldn't be loose. You may even want to unscrew it, then screw it back in, though be careful, as it's easy to mess up the copper wire in the middle of the connector if it doesn't insert properly when reattaching it.

A 3.1.1 error suggests a problem with the cable, though again, the reps will need to make the ultimate determination.

They may need to get some personal information from you in order to locate your account, but they'll ask for it to be provided to them via private message, for which they'll provide a link.