Unable to record from DJM-250MK2 to rekordbox

I am unable to activate the record button when I connect my DJM-250MK2 mixer to rekordbox on my mac or my PC. Rekordbox recognizes the mixer and the mixer's controls are paired properly with rekordbox interface (the decks say "external controller"). But when I press the record button, it turns red but the timer never starts and no audio is registered in the levels. 

I did not have this problem until a week ago, so I'm wondering if the problem was created by updating rekordbox? I have ensured that all of the settings are correct on rekordbox and have even tried replacing the USB cable that connects to the mixer. 

Many thanks to anyone who can help me with this problem!