No sound with HDMI

Audacity 2.1.2, MacOS 10.11.6, Mac Pro (trash can), 7.1 sound system via HDMI.
Audio output is by two devices: 1) HDMI to a Denon 7.1 decoder/amplifier, or 2) a MOTU 8M interface.

Audio via HDMI works fine on 8 channels from all other audio applications such as Pro Tools, Max, Ableton Live, etc., so it’s clear that 7.1 via HDMI is possible from all of those applications.

However, from Audacity, when HDMI is the chosen output device, no sound occurs (even though the graphic output meter shows sound output). Audacity works fine with the MOTU 8M, but no configuration works with HDMI. In the Audio MIDI Setup application I tried changing from 8-channel to 2-channel, changing from 24-bit integer to 16-bit integer, etc. Tried different data formats in Audacity (16-bit and 24-bit integer instead of the normal 32-bit float). Despite trying all permutations and combinations, no sound occurs.

Does anyone have any lead of why this combination of Audacity (on Mac), HDMI, and Denon decoder/amplifier does not work (while all other audio applications work fine)?

Did you try the ideas I suggested to you on feedback@?

1 Play audio in QuickTime before playing in Audacity.

2 Reselect the HDMI output in the Mac’s System Preferences before playing in Audacity.

Also look at the Denon help to see if it is set up to accept a stereo (2 channel) signal. As I explained previously, all Audacity playback is mixed down to stereo (or mono, if you have unpanned mono tracks). There is no multi-channel playback.