I left my boron connected to usb battery power supply for a few days to see how long the battery would last. The boron was working fine for several days. Then today I checked it and there are no lights.
Attempted holding reset button for 10s, 60s, holding MODE + tap reset per instructions, no success.
No lights are on. Acting dead.
GND to VUSB reads about 5v
GND to 3V3 reads 0, which is concerning
Device OS is 6.4.1
I'm a noob with all this - any help would be appreciated 
Thanks!
What happens when you power it directly by USB from a computer or external power supply?
It's weird that VUSB is non-zero but 3V3 is zero. That usually only happens when the device is in shipping mode. By default Device OS does not do this, but it can be enabled. You have to disconnect all power for several seconds, then power by USB or VUSB to get the device to start again if it is in shipping mode; no combination of buttons will get you out of shipping mode.
A hardware failure of the PMIC or 3V3 regulator could also cause the symptoms, which would probably be an odd coincidence because that problem is quite rare.
when I power via USB power supply, same exact symptoms
Then it probably is a hardware failure of the bq24195 or 3V3 regulator.
@Support can you help me start a warranty claim please?