For anyone else encountering Error 22 Battery Low, what worked for me is to SLOWLY charge the battery with an external 1S Li-Po charger using the Vbat pins.
I'd say it's save to assume the battery went into deep sleep / protection mode. The way to 'wake up' a Li-Po cell is to slowly and carefully, under observation!, charge the cell. Since it's only a 80mAh battery i recommend to charge it at 5-10mAh. Once the cell is woken up, the external charger can be disconnected and the internal M5StickC circuitry charge it from then on.
I hope that helps, this thread was in the top search results for me.

(I also tried connecting a 300 Ohm resistor between 3.3V and Vbat, but that wasn't sufficient even though theoretically it should work)