Mixing problem - no output

OK, that seems to make sense to me. As I think more about it, I wasn’t hearing “real” instruments in the imported midi file, just “wonky” carnival sounding tracks. I will look at applying rack instruments.
In this era of coronavirus, I am working with my grandson’s choir group and my wife’s orchestra group to produce “together” performances from individual files. The starting point is to get a melody track with a click track together that they can listen to and play/sing with, then time align their tracks all together and mix it in Cubase. It seemed like it might be easier to start by providing one main melody “instrument” from a midi file with a click track for synchronization. It’s a learning project…
I am 70 years old, started doing this stuff in high school with a tape recorder, razor blades and an editall block. Does anyone even remember tape?
GHW