Odd behavior- JRiver 27 and MacBook Pro not working right- no output to DAC

I currently run JRiver Media Center 27 on a MacBook Pro, and output that to one of two dacs available to me. This has worked for me for quite some time until now- something changed and I don't know what.

I go into the MIDI audio settings on my MacBook Pro, and select the output to go to the connected DAC. Once I engage 'play' on JRiver, my selected output on MIDI gets deselected and it reverts to "built-in output" even though my DAC still shows as an available output. And even stranger, when JRiver is running, I am not able to re-select the DAC on MIDI as an output, and somehow the DACs still see the computer as they show the sampling rate, whether its 88, 96, 192, etc. 

I don't know if this is a problem with my MacBook Pro, JRiver, or both! The same behavior is exhibited when using either DAC. Also, I am no longer able to set an audio output level on the MIDI set up page when a DAC is attached.

Any insights would be appreciated as getting an LP into JRiver  and then pushing play is about the limit of my computer audio skills. 

Thanks all