Since it beeped at the beginning, wouldn't it still at least beep even if the boost circut wasn't working?
If everything is working, it should always beep on power up. If it does not beep, it means that the processor is not running. Since the processor also supplies the signal that runs the boost converter, no beep means no boost.
So, something added after the beep test is causing the processor not to run. Take a close look at the solder joints added after the beep test. In particular those related to the low-voltage detect circuit (R1, R2, R5 & C10).