The strings were suddenly mute!  After checking what I thought was everything, key velocity, CC1,7,11; Finale dynamic markings etc... I found that as I was adding staves, I unknowingly went beyond the 16 available in a single bank.  When the strings got bumped to the next bank the "Bank Volume" Finale->MIDI/Audio->Audio Units Banks & Effects->Bank 2->Volume was set to zero.  I thought I'd mention this as something to watch out for when adding staves.