Sound not switching between VST instruments


I know this will sound trivial to most but basically I have just set up Cubase 9.I can monitor, record, playback audio.
I can add a VST instrument e.g. GA 4SE and Halion. I can monitor one of these (usually the first one I added) but can’t monitor the other. I have tried everything pressing the monitor switch, upping the level on the mixing console, changing midi channels but nothing.
I can even see the impulses when I hit the keyboard but still only sound on the other instrument.
I am using a UR242 interface which seems set up correctly.

Please help.


use REC button to chose what do you want to listen to.

Hilaroius! Yes, thanks, that did the trick.