DDJ RX no audio and mixer section not responding

I have an MBP Retina on OSX 10.11 El Capitan. Previously Rekordbox and the DDJ-RX have worked perfectly. I am preparing to record a radio and show and updated Rekordbox from 4.1.2 to 4.2.4. 

I then tried to use Rekordbox and got no audio, and also found that the mixer section of the program does not respond to input from the controller.

The jog wheels and hot cues of all decks still works, tracks appear to play, I can use the controller to load tracks to different decks and assign fx to channels, but no levels show on the mixer and there is no sound. 

When changing the system audio output to DDJ RX and playing system audio, no sound comes out. 

'DDJ RX is connected' shows at the bottom of the screen. In Rekordbox preferences, The DDJ RX is selected under the audio tab.

I then downloaded 4.1.2 and installed it to see if it would fix the problem but it did not.

I reloaded the firmware version 1.03 (the same as I already had) in case it had got corrupted and this did not help.

I have run disk utility and first aid on my drives and no errors were found.

Without the DDJ RX plugged in, Rekordbox works fine and sound comes out of the internal speakers. As soon as I plug in the DDJ-RX, all mixer settings are reset to zero, sound stops. Even if I change audio output to built in, no sound comes out.

Now I'm really stuck. My deadline to deliver is tomorrow. Please help.