ESC/PIXHAWK powering problem

I have a new problem with the powering of my rover.
I use a Pixhawk cube and 2 ESCs for brushed motors (xcar 45A).
When I connect the pixhawk to USB it starts well. All the components start without problems (Gps, buzzer, telemtry and RCin).
The problem arises when I connect the power board to battery (Turningy 4000mAh 3S 11,1v). In this case only the 2 ESC’s leds starts while the pixhawk and all components don’t start.
Today is the first time that the problem arises.
Does anyone know why?