Broken microphone on Enviro+ FeatherWing

I’ve noticed for a while that my Enviro+ FeatherWing always plots a flat line for mic/sound. I’ve just checked and the standard deviation sits around 55 regardless of audio level in room which suggests it’s just reading electrical noise rather than sound although the level is around 32768 (half way)? I’ve even tried tapping it with same result. Is my microphone broken?

Adafruit CircuitPython 6.0.0 on 2020-11-16; Adafruit Feather nRF52840 Express with nRF52840
>>>
>>> import analogio, time
>>> import pimoroni_physical_feather_pins
>>> import ulab
>>> import ulab.numerical
>>> mic = analogio.AnalogIn(pimoroni_physical_feather_pins.pin8())
>>> samples = ulab.array([mic.value for _ in range(10000)])
>>> ulab.numerical.mean(samples)
32841.8
>>> ulab.numerical.std(samples)
53.2202
>>> ulab.numerical.max(samples)
33088.0
>>> ulab.numerical.min(samples)
32624.0

microphone.py example also doesn’t work but that’s not surprising given the above.