Play button don't show up on Serato Dj with it hooked up to Pioneer DDJ-Sx2

I just purchased Pioneer DDJ-SX2 this week. I have a MacBook Pro, I use Serato DJ but when I hook up the DDJ-SX2 board to my Mac the play button doesn't show up on software. Also, the play button on the DDJ-SX2 just keeps blinking and it won't let me hit play either. All the lights show up on the board. But won't let me play song. .