Error 1001 usually means the box can't get on line. This is most likely a cabling issue (make sure the cable that was in your old Horizon box is now in your new one, and it connects into exactly the same hole-in-the-wall as before) but it could be a provisioning issue.
UPC provision your services using an identifier (probably a MAC address?) of your box. This is how they can, for example, kill internet and landline on a Horizon box and enable it on a Connect Box or other modem.
Provisioning sometimes sorts itself out in a few hours but if not you'll have to call UPC. But do give your cabling the once over first.
If you can disconnect the new box, plug the old box in using the same cable and it works, then either the new box is faulty or it somehow has to be activated. I agree with your assessment.
Hopefully it gets sorted when someone comes to see it. At least you have an old box to use to get online while waiting for them!