I use a Denon 1601, and I had a similar problem. All I had to do to correct it was to reset the "input mode" to the "auto" position which selected the digital input -- somehow it had gotten switched to the "analog" input mode.
If that's not it then you might have to reinitialize the microprocessor as per the instructions in the manual, but try the above suggestion first. Let me know how you fare.
If that's not it then you might have to reinitialize the microprocessor as per the instructions in the manual, but try the above suggestion first. Let me know how you fare.