Onkyo TX-NR575 only 2 channels from PC HDMI Output

I am having a very strange problem with my Onkyo TX-NR575 receiver when connected to my PC.

The PC has Intel High Definition Audio HDMI chip to provide a 7.1 channel output. When I connect the PC to the 575 via HDMI, the PC states in its sound settings that it only has 2 channel stereo with no choice for 5.1 or 7.1 output.

If I unplug the HDMI cable that comes from the PC and goes to the Onkyo TX-NR575 and plug it into my Denon AVR-X4400H, I get 7.1 in the PC sound settings.

For some reason if the PC is connected to the Onkyo, the PC thinks it only has 2 channels. Without doing anything except unplugging the HDMI cable that comes from the PC and goes to the Onkyo and plugging it into the Denon instead of the Onkyo, the 7.1 choice becomes available in the PC sound settings.

I'm thinking that the Onkyo just can't decode the signal passing through the HDMI cable and the Denon can.

I'm stumped. Any insight from anyone? I'd appreciate any and all help.

I don't use the Denon in my system because it has handshake issues with my Samsung Q9F 75" TV. The Denon refuses to pass HDR to the Samsung even if set to do so by using the enhanced HDMI option. I just get a no signal screen. The cheap Onkyo however works fine with HDR. Go figure.

Thanks