What to do when Matek F722-STD flight controller is not booting without connected battery and connection from Configurator is not working? Simple, power GPS and magnetometer from a different pad.
All 5V pads are powered only when external power is supplied to the flight controller. Not when power is applied via USB cable. If you connected GPS and magnetometer to 5V pad, it will not work and screw I2C bus up. To solve this problem, connect GPS to 4V5 pad instead!