Well, i have exactly the same problem with mine.
Bought a defective one g2. There is no light blinking, neither in the power button nor the charging port. I loaded the Batterie up to 3.5 volts externally, tried the reset procedure, but still nothing happening.
The only thing the FlirOne does, is charging with around 4 volts after pressing the power button for (around) 10seconds.
I also loosened the 5 torx screws, but found nothing special/defective on the circuit board.
So if you or someone other have the solution for this problem, i would be very grateful to hear from it.
Thanks