DDJ-400 no master sound output to Mac usb device

I know this seems to be a common issue and believe me Ive searched the forum to find a solution, but ive had no luck. 

I have audio in my headphones but no Master out. Im using a MacPro with Catalina and I want Master out to my Bose Companion 5 USB speakers. I dont think this unique just to my MacPro as ive also tried to get this working on another Macbook Pro and have the same issue. 

Im pretty sure I have all the correct settings that everyone mentions... 

- Audio in Rekordbox is set to DDJ-400

- Output channels - Master output=DDJ-400: Master, Headphones Output=DDJ-400: Phones. 

- Mac's audio output device set to Bose USB Audio

- The Audio MIDI setup - rekord aggregate device - has Bose USB and DDJ400 audio boxes both ticked. 

- both faders are up and checked all knobs. 

One strange thing ive noticed is when i hit the PC Master out button it appears to turn on for a second then turns itself off again. This is the same when I check the box within preferences, again the box appears checked for a second then turns off again. The exact same issues happen on anther Mac. 

Anyway im hoping someone can help here - surely we can send audio out to a USB device connected to a Mac? thanks in advance.