No digital stereo sound but digital 5.1/7.1 works

I had a weird problem with sound, I wasn’t getting any from my PC.
I was watching tv and I switched to my PC (HDMI -> tv=sound) but I didn’t get any sound.
The first thing I checked was the output wasn’t muted in the PulseAudio Control.
It was unmuted but no sound so I rebooted.
Still no sound so I looked around the PulseAudio Control.
I was trying different things and I changed the Configuration/GP107GL… (my video card) Profile to “Digital Surround 5.1 (HDMI 2) Output”.
7.1 also works.
Stereo does NOT work.
Does anyone know why stereo wouldn’t work?