"Sum multichannel outputs to mono in Source Monitor" not working

My audio mix levels are fine and the volume bars are moving on the correct channels. When I export ProRes with 8 channels and open in QuickTime, I can hear them all. I just can't hear them in Premiere on the timeline. I can only hear channels 1 and 2.

MBP M1 Max, masOS 13.3.1 (22E261)

Premeire 23.3.0 Build 61