Xi-6A wireless box playing rear surround sound through front Dolby Atmos speakers

I cannot figure this out. I have a Dolby Atmos system consisting of two front speakers, center channel, double subwoofers, two rear surround speakers and two front Atmos speakers. My Xfinity Audio is set to expert mode. I should be able to get Atmos enabled content from Netflix. I can’t. When I open Netflix, the Atmos logo isn’t displayed on content I know is available with Dolby Atmos. Everything just says 5.1. If I go to Netflix through my XBOX, there it is, the Atmos symbols. When playing any and all content on Xfinity that isn’t streamed, my rear surround speakers are silent. What signal is supposed to be going to my rear surround comes out my atmos speakers. I’ve checked and rechecked my wiring to my Marantz 9.1 capable amp. It is all correct. If I go to YouTube via the xfinity app and run a sound check video for either 5.1 or 7.1 sound, the rear surround speakers are silent. When the video says, “This is the right rear channel,” my right Atmos speaker fires. When I stream Netflix or Amazon, 5.1 content, the rear channels work. It is very frustrating.