audio problem

I have the rekordbox 5.3.0 on MacBook Air 13" 2017 and xdj-rx2 connected with a usb cable that came with the xdj-rx2, everything is working fine together on performance mode except the AUDIO(no sound), then I went to the settings-audio-driver to install xdj-rx2 but there's still no sound but for export mode, there's sound. why please?