Can't play through KRK Rokit 5's

Hi, 

I have a DDJ 1000, a 2020 MacBook Pro with Rekordbox version 6.5.0 installed, and two KRK Rokit 5 powered speakers.

My problem is that I cannot play through my Rokit speakers. In Rekordbox Preferences the only audio option that comes up is my MacBook Pro speakers. 

Please can you advise on what I should do?

Thanks,

Alex