Check your cables to ensure they are tight. If they are, Call Comcast and ask them to send 1 of 2 hits to your box. If you have a SA box, have them send a "BOT" if you have a Motorolla box, have them send a "INT" if neither works, you need a service call.. don't let the rep tell you to go down and swap the box. Have a service tech come to your home and check inside wires and or splitters.
The TV cable connection in my upstairs home office is constantly blinking out. I get the black screen which says this device is not activated. I only have this problem on one TV. I move the little box from my office to my guest room often. Regardless this should not be a problem. Please advise of fix