I have an HD set top box. I connected it to my new HD TV with a new HDMI cable. All channels come in just fine EXCEPT the HD channels. None of them come through.
It says that it does not get the signal. I spent half an hour with the TV technical support going through tests and they said this is a problem with the signal, not the TV.
If its a problem with the signal then they have to send a tech out and find out where the issue is.
Check any splitters you have as they can cause signal issues.
Do you have another coax outlet to test it on to rule out a coax issue?
Another possibility is an HDMI hadnshake issue between the box and the TV. I know there was an issue with some sets in the past, don't know if it still exists.