Rover 4.0 and brushed motors

I have a rover with brushed motors and bipolar ESCs. I believe that I have set all parameters correctly, but the motor test doesn’t work.
when I attempt to test the motors the Pixhawk 2.4.8 rapidly cycles the man LED through red, blue green, for the duration set for the test, which I understand is code for ESC calibration. The motors do not spin. Mot_Pwm_type is set to 4. I know the wiki suggests 3, but that doesn’t work either, nor does 0.
The main LED is solid blue, as it should be, I am not using a GPS.
The motors work fine using a servo tester.

Any ideas?