Mac mini, explorer2 - exclusive mode not availabe

Why would exclusive mode not be available when using an Explorer2? I can’t seem to find a combination of settings that will enable it and I don’t know why it would not work.

The same track playing on a different mac mini using optical output to my AVR show exclusive mode is working,

Is “Use Exclusive Mode” checked on the playback tab of audio settings?

I just knew I was missing something that should have been obvious. Thanks for pointing me in the right direction.