DDJ RB I tried to turn update mode on but nothing happen

Before running the program you should set the DDJ-RB in update mode: Press and hold the USB cable while pressing the SHIFT button and the SYNC button on the left deck.  If the update mode is activated, MASTER CUE led flashes. I have try to do all these step but the master cue bottom never flash, how long ever i press it, what I have to do? Please help!