Cubase 11 and URC44 Control Room Set-up

I have a URC44 interface and two sets of speakers.
I want to use the control room to switch between the speakers.

In the audio connections window I have set the stereo output to not connected.

In the control room tab of the audio connections window I have set-up two monitors.
The first one is connected to UR44C Mix 1 L and R and I get sound on the main speakers.
They are physically plugged into the main output jacks of the UR44C.

My problem are the second monitors, connected to the B button in control room. In audio connections Monitor 2 is connected to UR44C Mix 2 L and R.
However, when I click on the B button in CR I get no sound, regardless if I plug the second speaker into the Line Output 1 or Line Output 2 jacks of the UR44C interface.

How do I have to route the monitor 2 outputs in the audio connection window and into which jacks of the UR44C do I have to plug my second set of speakers to get sound when I hit B in control room?

I have UR44 (original, not C) but I believe the routing is the same.
Mix bus 2 is connected to Line Outputs 3/4.
Line Outputs 1/2 are the same as the Main outputs jacks, just without passing through the Volume control on the UR.

Thanks a lot for your reply, robw.

Unfortunately I can’t get Mix 2 L/R (or output 3/4 if you will) of my URC44 to work. Even if I switch off the control room and set them as stereo out, still no sound.

Any ideas? Or is my URC44 broken?

So here’s an old post with brief description of my setup. Note I’m using Control room so Mix 1 is my Mains and Mix 2 is my headphones - but the same principle applies. The full thread has a few links to youtube videos which may have more details. I thought I had an old post with actual pictures describing the full configuration. This question gets asked quite a bit so you may find some more youtubes and posts on the topic. Anything UR44 (not C) will apply to your device.