headphones flx4 problem

I have a problem with my newly purchased Pioneer DDJ-FLX4. The headphone audio isn't working. In the audio settings of Recordbox, I've set it to DDJ-FLX4 WASAPI, and for the output channels, I've chosen DDJ-FLX4 WASAPI: PHONES. When I press the button on the mixer for both deck 1 and deck 2, it doesn't work. However, when I press the cue button on the master, I can hear the audio in the headphones. I don't understand why this is happening. Can someone help me?