Disclaimer: Do the following procedure at your own risk. I'm not a Comcast insider. I'm just good at debugging.
Symptoms
Your cable box has lost signal without being able to recover. Comcast’s customer support has sent a reset signal, but the box is not responding to it.
Problem
What I believe has happened is the box has lost trust in Comcast. Now it refuses to accept any signal from the remote port including a reset signal.
Solution
The solution that has worked for me is to deactivate the box, and then to reactivate it.
Procedure
1. Reset/deactivate the cable box:
- Press and hold "0" on the remote control for about 5 seconds until the diagnostics menu comes up.
- Quickly press "1", "3", "7", "9". This will reset/deactivate the box.
2. Wait until any visual activity stops. Reboot the cable box.
3. Verify the box appears as "not activated":
- Press and hold "0" on the remote control for about 5 seconds until the diagnostics menu comes up.
- Switch to the item that looks like "DTA status" and click on it.
- You should see something like "Activated: No".
4. Call Comcast (or do it over an online chat - it's much faster) to ACTIVATE your box. You'll need the serial number of the box which is printed on a label on the bottom of the box.
Within a couple of minutes, TV signal should come in.
