Hi Ernie,

When you click on the MIDI In box, does nothing happen at all, or does a blank rectangle drop down? If a blank rectangle drops down, there's a chance that selecting it will work. Some devices will be listed but with no name sometimes.

That being said, according to M-Audio, the Oxygen 8's latest driver only official supports Snow Leopard or earlier:

http://community.m-audio.com/m-audio/topics/oxygen-8-driver-for-osx-sierra

Some people in that thread did report using the driver in newer operating systems, so you could try installing it anyway, shouldn't hurt anything.

Thanks
Kent
PG Music