Pi-Zero upgrade problem.

[AF6VN]

OK..here is what happened. I took your advice and booted the Zero from my 3B ac supply. Bingo!..Booted up. Then I restored the config file. Shut down and rebooted from the battery pack. Works fine! Now why did I need to kick start the Zero from the ac supply? Booted several times now from the battery pack and it is still working just like it always did.
Thanks for the advice. Now if I could only restore my hair I lost in the process.
K2TL

Normally Pi-Star runs in a read-only configuration, but a first boot may need to transition into read-write to move some configuration information around. Writing takes more power than just reading (the documentation for BeagleBone Blacks explicitly recommend using a 5V wall-wart when reflashing their on-board eMMC chips, due to the power consumption).