I think you use a preconfigured I2C cable with JST-GH 4 pin connectors on both sides, so you can not swap anything with that cable.
Just for information: I soldered a JST-GH to DF13 cable since i use a pixhawk 1:
1 (red) VCC +5V
2 (black) SCL +3.3
3 (black) SDA +3.3
4 (black) GND GND
I just checked the messages if you did not connect the sensors:
There is no error message ! (ArduPlane V3.8.5beta1 )
if it also does not work with PX4 stack, i would turn to drotek
Regards Rolf