Analog Voltage reporting error on Feather ESP32 V2 (A0) - analog calibration data missing error

When testing the analog inputs on the Feather ESP32 V2 in combination with the Simple Soil Sensor, I was only seeing 0.00 reported, even in raw mode it reported 0. Looking at the console the milivolt reading function was reporting a log message of something like "err: adc configuration data retrieval failed".
This was repeated for each voltage reading (not raw readings though).
It's probably an artifact of switching the voltage reading method to use the calibrated conversion function (analogRead-Millivolts).

In the end my breadboard connections were loose / bad. I switched to A2 input instead of A0, along with getting better connections setup. Then / now the readings are coming through appropriated, both in Raw and Millivolt readings (on A2).

Not sure what the situation is, but we could potentially catch or report the adc calibration error (and fall back to the older method of scaling raw value across the VCC/bit range).

Reproduce the analog voltage readings on a Feather ESP32 V2, comparing A0 and A2 in raw and millivolt modes, and inspect the calibrated millivolt path associated with the ADC configuration error. Done means the calibration failure is consistently handled or reported and the affected readings have verified behavior.

Written by the indexing model from the issue text.