This is a common problem with Onkyo units. The HDCP signal encoded into the HDMI output of the cable box is not able to be passed through the Onkyo.
Sometimes you can get the signal to "handshake" and play nice by powering up the components in a sequence. The sequence is, power up the TV first wait 2 minutes, then the Onkyo, wait 2 minutes, and then the cable box. This sometimes works, but it is very redundant and inconvenient.
Unfortunately, the only other solution is to bypass the Onkyo's HDMI jacks altogether, run the HDMI straight out from cable box to TV, and then run an Optical cable from either the Cable Box, or the TV back to the Onkyo for the Onkyo to decode the surround sound information for playback.
I wish there was another solution, but I've seen this issue scads of times with Onkyo units and it is a problem from the manufacturer.
If you need further assistance, let me know.
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