I assume you are only connected to one television. Check your HDMI cable and coaxial cable for tight connections.
I would unplug the cable-box for at least one minute. Plug it back in and give it about 5 minutes to reset and down-load coding from Comcast. Turn the box back on and make sure the television is set to the correct HDMI input to get the signal.
The cable-box circuitry can fail and block output through the HDMI output. You might need to exchange cable-box and remote at your nearest service center for a "no charge" replacement.
Return both remote and cable-box for exchange. They will exchange it right there with no hassle.
I have done it a number of times. The boxes are cheaply made and fail rather often.
Yes, i am connected to one television. I checked HDMI cable for tight connections. Also checked the cable with other devices, it works with them. Tried other HDMI inputs on tv. Also disconnected everything, rebotted cable box etc. None of them worked. Only AV cable works. I assume id has to do with HDMI output of the cable box. Comcast not helpful at all. Can i just take the cable box to the nearest service center? Thanks for your reply.
Apologies for this issue and the experience that you described above.
Providing the address and hours for the service center near you below. I've also asked a colleague to look at your account to see if his is something that can be corrected without a box swap:
13529 Connecticut Ave
Silver Spring, MD 20906
Hi ozgurezel, I am showing that you worked with replacing the cable box with our Team on Twitter, and looks like everything is working properly. If you have any other questions or concerns please let us know.
Success! I followed the directions to unplug the cable box and tighten the cables, and then took 1 extra step. HDMI still showed no signal and the xfinity remote didn’t work. I used the TV remote “input” button to change to HDM2 and the problem was solved.