I went there and chose ADAT 1 (1 + 2) as the default setting.  There is a green check mark by it, showing it as the default.  It was the only one with the meter showing a signal present.  Still no sound coming from the speakers.

I'm sorry but I'm not sure what you mean.  Cubase sound comes out of the same speakers (routed through an amp and the Fireface) that all the rest of my computer sounds come through.  With my old audio interface (Focusrite 6 usb), I had the same setup and all the sounds-Cubase as well as Audacity, games, etc. would all come out of the speakers fine.  Now only Cubase does.

If you already understood this to be the case, my apologies. 

I tried choosing every possibility in the sound area of control panel to be the default, none of them work.  Only one of them shows a signal on its meter but it doesn't work either.  So perhaps I need to re-route the audio through the mixer as you suggested.  I'm a complete noob with the mixer--can you give me any suggestions as to how to do that?

Okay thank you for your help.