VST Instruments Are Not Working.

Hello,

I recently downloaded Cubase onto a new laptop. It is a MAC Book Pro, 2.5 GHz with Core I7. Wen I try to play my VST instruments, Omnisphere and the instruments that come with Cubase, I do not hear any sound. I can open all on the instruments and edit their features. The transport panel says that I am receiving MIDI signal. In Halion, even I manually click the notes, still no sound is produced.

Update: I use my Behringer X32 as my studio interface. When I am plugged in to the X32, the instruments do not work. When I am unplugged from the X32 and running on built in audio, the instruments work.

Thanks,
Matt.