I know this is old but found it while searching. This just happened to me (last day of 2020,naturally--perfect end to the year). In checking around, it seems that the HDMI boards in these units have this problem and are no longer available, so that $500 repair described above (board replacement) is not possible. It appears possible to send it to "United Audio" for a manual repair (they replace components on the board) but
not worthwhile for a 2013 AVR without Atmos and bare 4K support.
It's a shame because the unit sounded terrific.
I unplugged it for 30 seconds, no change. Did the full-on microprocessor reset from the manual and managed to lose all my settings (not unexpected). No change--HDMI video fine but no audio over HDMI. Finally, found instructions online for a soft reset: turn it off, unplug the power, and (maybe most important) unplug all HDMI connections overnight.
Lo and behold, that fixed it: HDMI sound is back, although it went through the startup again, asking about my configuration. Since it's time for an upgrade, I probably won't bother with the re-calibration.
I unplugged it for 30 seconds, no change. Did the full-on microprocessor reset from the manual and managed to lose all my settings (not unexpected). No change--HDMI video fine but no audio over HDMI. Finally, found instructions online for a soft reset: turn it off, unplug the power, and (maybe most important) unplug all HDMI connections overnight.
Lo and behold, that fixed it: HDMI sound is back, although it went through the startup again, asking about my configuration. Since it's time for an upgrade, I probably won't bother with the re-calibration.