Why is it irrespective of what Radio I select the Transmit Audio Source insists that it is Front/Mic?

How can a microphone input become an audio output?

The choice to make the source the data socket on my FT-450D is permanently greyed out.

The older WSPR program works like a treat but I'm close to calling it quits trying to use the new WSPR or any of the other digital modes in WSJT-X.

I may be way off track in what I think the problem is so any help/suggestions welcome.

Merv VK6BMT