Blheli_s 4in1 along Pixhawk, Motor doesn't wanna spin

Our ROV setup is containing BRF2838 BLDC, 4in1 blheli_s ESC (Racerstar ESC for FPV drones), pixhawk 1 (ardusub 4.0.3) etc.

  • How to test a single motor from MP? We couldn’t really find a way.
  • We have managed to test from QGC for a single motor, and it is spinning like 30 rpm and I don’t know why? Isn’t ESC compatible with Ardupilot or something about the firmware wrong? ESC firmware is blheli_s J_H_90_REV16_7, ESC firmware is flashed for bidirectional (1100, 1500, 1900), PWM parameters of ardupilot, min-max and protocol(DShot600) is compatible with the ESC.
    Btw plugging off the ground wire doesn’t affect the spin at all which is strange.

Maybe it’s stupid but I had a similar problem. The battery voltage was too low for 2S and the motors were turning very slowly. When I used the 4S battery, the motors started to spin.