That's a hard one, Its as if something hasn't been enabled or properly configured, which could be your sound card, your midi config on the Virus, Novation, and computer, the wrong settings in cubase, or the wrong setting on the Virus.
A few things to check:
Via the Virus menu, have you assigned the outputs on the Virus Classic (for the patch or multi you are using) to output 1 (L&R)?? The outputs might be set to something else, like Outputs 2, or 3, or Surround sound. This is a fairly common oversight. Also check that the Global midi channel for the Virus is set to the same channel in Cubase and the novation. You can also set it to `omni'.
If that's all good, then carefully check your settings in cubase. You said you created an Audio/midi track? There is no such thing- it will be audio OR midi, and each type will require your track to be configured differently. Its very likely that the problem lies somewhere here. Check the input and output routing for your track, and also for the project.
Also, check your overall midi and sound configuration on your computer.....look for things like muted channels, and check that your control panel/the sound card is set up correctly, for midi and audio.
If you want to do just a quick test to check that your Virus classic works, you can audition the sounds directly on the Virus Classic (check the manual to see how, but try pressing down the two buttons above the display together)). Another way to do it would be to plug the Virus outputs into your amp/speakers/monitors , and then plug the midi out of the Novation into the midi Input of the Virus classic. Check that the Virus Classic is set to receive midi on the right channel (or use `omni'). Check that the patch/multi is assigned to the outputs plugged into your amp/speakers. You should be able to play your virus classic this way.
Hope some of this helps. Just be very thorough, and check things sytematically. It might feel frustrating, but you'll learn a lot going through this process.