no audio on the headphones and master left - right

good evening

I just got my FLX4. I am really new on this. I switch ON the DDJ FLX4, then connect the pc to the DDJ FLX4, then start the SERATO DJ LITE app and everything seems to be working but I dont have audio neither headphone nor the Master, I tried the the speaker and headphones on diferentes devices and they sound ok, I can listen music normal.