Ensure the M1+A1 are properly paired. When both the M1+A1 are paired, the LED will be blue on both of the units. If they are not paired, press and hold the Bluetooth button on both of the units for at least 3 seconds to start pairing.
If both of the unit are paired but there's no audio. Make sure the firmware for the GoPro camera is up to date and the A1 Mini-USB connector is working properly.