Rekordbox 5.7 does not support XDJ RX headphone output

Hello,

I installed Rekordbox 5.7 on my Mac and the newest driver / update on my XDJ RX.
As I want to use my XDJ RX as a Midi controller for Rekordbox, I connected it to my Mac. 
Now the problem is, that I can't choose the XDJ RX for the headphone outout, so that it's not possible to pre-listen the songs.
I also trryed it on another Mac with Rekordbox 4.5, where everything is running.

What is the solution?

Thank you!