Hi Michael,
As far as I know, no support was added or dropped in the latest X-Plane updates. What seems telling to me, in the details you provided, is that you mention you recently upgraded to a new computer running El Capitan. We have had numerous reports of USB device issues with this OS & X-Plane.
You also mention that "MHW adaptor is no longer in the device list." I am not sure where you are seeing this. Can you provide a screenshot of where it was in an older version?
It sounds like you can see the axes in the Joystick & Equipment screen but they do not respond. Did you have the USB adaptor plugged in when you started X-Plane? Please try unplugging it and starting X-Plane, then plugging it back in to see if it then recognizes the axes.