Motors suddenly not responding

Hello there,
I am facing an irregular problem with my Pixhawk. I have been using the flight controller for about 2 months now and I am using an RC transmitter manually control the drone.

The current flight stack I am using is 1.7.3 stable release.

Everything was working normally last week and I left my quadcopter completely untouched for the weekend. Coming back to it today and I found out that the motors no longer respond. I am able to arm the drone using the transmitter and through QGroundControl but the motors do not idle spin nor does it respond when increasing the throttle. Even the usual twitching does not occur when I connect the battery. I have checked that the Pixhawk, PDB, and RC receiver are turned on as usual.

I have tried to reflash the firmware and recalibrate everything including the ESC but the problem persists. A loose wire might not be the problem as all 4 motors are not responding. Could there be a problem with the power supply or is the Pixhawk having connection issues?

Update: I used APM Planner to flash Arducopter firmware and all the motors worked fine after calibrations. After that, again I flashed the PX4 flight stack using QGroundControl and calibrated everything but the problem still persists.

To me this sounds more like a Problem with Power Supply. What happens if you disconnect the Motors from the Flight Controller? What ESC do you use? What PWM Signal Type are you using (regular, OneShot)? What are your PWM Settings for the MainOut PWM Connectors?

I use Hobbywing BLHeli ESC which need a Powerup Sequence from the PWM Signal in order to Arm.