fuel.getSoC() fails

After running for several months my electron started returning 256 from a fuel.getSoC() call. After about a day it now returns 0, or maybe nothing, it’s hard to tell.

Since I have a battery check in my application that turns off the electron if SOC is below 20% the electron keeps turning off every time I restart it with a reset.
I tried 2 batteries, both of which show approx 4 volts with a voltmeter.

It runs in safe mode and I loaded Tinker, which works fine.
A check of vitals in the web console shows “No battery charge data for this time period” for battery.
Any ideas?