FLAC and 7.1 Audirvana 3.5

My system is as follows;
Windows 11, ASUS TUF Gaming Plus Wifi MB, AMD RX6600 GPU. My AVR is a Marantz RS7015, speaker array is 7.2. Audio plays through RX6600 - HDMI to the AVR, video is from AVR to Samsung 55 inch curved TV. When I configure the sound in Windows to 7.1, Audirvana will not play FLAC files. If I configure the sound to 5.1 then it does play these files. Other apps like Media Player Classic play these files just fine either way. Anyone have a clue as to why this is?

Do you get an error form Audirvāna when you have this behavior?