Trying to set up a TV in the spare bedroom. We have a spare cable box from before we became empty nesters. I reconnected the cable box to a TV in the spare bedroom. I can turn the TV off and on with the Xfinity remote. However, the TV is not displaying a picture. I double-checked the connections, and the input source of the TV is set to the cable box. According to our bill we are only paying for two boxes. So I assume that this particular box needs to be reactivated somehow. How do I go about doing that?