Stereo Out won't work

Hello there,
I am trying to set up a session, in this case Ambisonics, but could be anything, also simple stereo.
I have the 3rd Order Ambisonics and Stereo, active in my Audio Connections Output. The Stereo Out is selected as Main.
In my Mix console I have both 3rd Order Ambisonics and Stereo.
When assigning any tracks, of any format, to Stereo Output, it won’t show any levels (and I won’t hear it).
If I’ll assign any tracks to 3rd Order Ambisonics (and making it Main Out), it will show levels and I can listen to it.
What can I check to make the Stereo Out it work, please?
In my Studio Setup, all my I/O are active.

Nuendo 12.0.50; Mac OS 12.6.1

Thank you in advance.

For some reasons it stopped working on all my sessions.
I started a session from “Empty” and rebuilt from scratch, and now it works, so I have to reimport my other sessions into that.

There are many reasons why things sometimes don’t work out right away. Especially when a project is very complex. To help from a distance is unfortunately very difficult. Therefore nice that you could solve the problem yourself. :+1:

Thank you.
Settings are exactly the same in all sessions. I just got some ghosts hidden somewhere.

Have you tried to remove the stereo bus and then add it again?