Losing.1 sub when Rendu feeds Oppo

For some reason when I choose the ultra Rendu in Roon I loose the feed to the subwoofer.

Any ideas why?

so the usb input on the opp205 bypasses all processing. I’m sending the signal through the multi channel outputs to my Onkyo receiver’s multichannel inputs. The Onkyo also bypasses processors in this mode.

I can use the stereo outs of the Oppo to a stereo in on the Onkyo. Then I get the subwoofer output fine. But to my ears the multichannel input sounds better and I would like to find a way to pull some bass from that feed.

Maybe this is the wrong forumm, since it isn’t really Roon issue , apologize if so.