Unable to Trigger Halion Sonic via USB

Hi there fellow Cubase users,

I have a Mac running El Capitan (10.11.6), Cubase AI 8 and the Halion Sonic SE2 Plug-In. I am trying to use my M-Audio KeyStudio 49i keyboard to play the sounds in Halion Sonic SE2 Plug-In directly, so I can hear the audio output from the Halion Sonic SE2 Plug-In as I play the KeyStudio 49i keyboard. I have the KeyStudio 49i connected to the Mac via USB. I can see that Cubase is receiving MIDI from the keyboard, as I can see the MIDI In Activity level indicator on the Transport panel responding as I play the KeyStudio 49i. I can also record MIDI events on a track in Cubase with the KeyStudio 49i and play those events back with the sounds from the Halion Sonic SE2 Plug-In, but no matter what settings I play with, I cannot play the sounds on the Halion Sonic SE2 Plug-In “live” with the KeyStudio 49i keyboard.

What I have also found is that I can play stand-alone software instruments such as Arturia Minimoog V and Arturia CS-80 “live” just fine, but whatever I do I just CANNOT play the sounds on the Halion Sonic SE2 Plug-In “live” with the KeyStudio 49i keyboard no matter what I try.

Any suggestions or help any of you might have with this would be most welcome. Thank you.