UR28M configuration help needed.


I´d like to get some advice on this config scenario:
I have Yamaha HS7 and multimedia speakers and one pair of headphones set as cue for performer listening.

Yamahas are routed to MIX 1 LR - ouput 1 L R
Heaphones are routed to MIX 2 LR
Multimedia speakers are routed to MIX 3 LR - output 3 L R

Everytyhing is working fine so far and in order to switch between the speakers I press the A and the C buttons on the UR28M

Now,I wanted to create additional speaker output at the control room setup. And then be able to toggle cubase control room monitor buttons. I can´t get this to work. I just created another speaker assignment and routed it to mix 3 but when pressing the soft montitor button in cubase there´s no sound.