HD-DVR Channels "Temporarily Off Air..."

HD-DVR is not receiving a vast majority of SD & HD channels properly.
Keep getting a "Temporarily Off Air...check back later" message on many channels.

Channels are changing...for example HD Channel ## will get fine reception then later will display "Temporarily Off Air..." message.

Service & Install was on 23 Oct... problem has persisted & gotten worse since that day. I have gone thru the trouble shooting steps as recommended on Cox TV Support website with no success.

Conducted two (2) DVR Box Resets today...problem got worse after each reset (i.e. fewer channels receiving properly after each reset)

HD-box (non-DVR) in other room in house works fine.

Greatly appreciate any guidance/support.