I recently bought a betafpv hx115 and flew it for roughly 20 batteries with no issues. Last time I flew everything worked fine until I tried to fly it today I don't get all the tones or lights when I connect to lipo only.

Problem:
With lipo I only get a red led and only the first tones, my rx doesn't power so I assume it's something with the power.
when I connect lipo and USB everything seems to power and function normally.
from what I gather this is something to do with the 5v reg or maybe the 3.3v reg? Why do I get anything at all if a reg is blown? Can someone help me diagnose what the actual problem component is? I have a hot air station and donors to try and fix it.

FC&ESC：Toothpick F4 2-4S 12A AIO FC

First thing I do is measure the voltage on the 5V pads with lipo. If you don't get 5V, then it is likely the regulator or schottky diode. Report back with your findings.

Thank you, I will do that.