HDMI output doesn't work

MacOS: Monterey (12.3.1)
Audacity: 3.1.3

Both my office and the classroom I teach in have HDMI outputs for audio. The HDMI devices correctly display in the pull down menu, but when I select them, no sound comes out.

I’d be grateful for any suggestions.

Can you play audio from Music/iTunes through the HDMI?

Make sure, when using Audacity, to connect the HDMI before starting Audacity. Also try Transport (menu) > Rescan Audio Devices.

– Bill