There is a bug in the AXP2101 begin() logic which means the Core2 V1.1 doesn't start on DC power.
The current official fix, along with my variant can be found here https://github.com/m5stack/M5Core2/commit/c26f1b63635c90d9bd82d87db6ab4d9048b3a1b5 .
Both check to see if VBUS is powered before deciding whether to enable the DC-DC converter. The original V1.1 behaviour is to always enable, and this causes an error shutdown from the AXP2101.