I use a MacBook Pro, OS High Sierra 10.13.6.

I'm writing an 8-hand piece for two pianos and the notes below G2 (or so) aren't playing back, or if they do, they're SUPER soft. 

I'm using a Yamaha P-80 for input and have no other devices connected. Generally I use the " Play Finale Through Audio Unit" setting, however, I've tried switching to the Playback through Midi" option. It doesn't seem to make a difference. I get no bass notes either way, but hear all the other notes loud and clear.

I've used this same set up for LOTS of projects and not had this problem. Could it be the latest Mac update? (I saw an email come through from MakeMusic saying that bugs were worked out with the new update, but maybe they're not?)

Any idea of what's wrong or how to fix this? 

Thank you!!