First of all, yes I have gone through droves of posts on XDA and frankly it’s a mess, but I can tell you that after following a few threads that just refer to themselves in loops, there’s no actual solution.
I have an LG US730 which was rooted and everything was great. I must have toggled something in SuperSU - I think maybe the option to be rooted during boot.
Anyway, now all I get is Security Error and it shuts off. None of the recovery power on switches will work. The only thing I could do is VOL+&- power while the usb is plugged in and it goes to a download in progress screen. Of course nothings happening and I need to remove battery in order to get this powered off at this point.
Anyway, I’d love if anyone has a tool to repair this. LG’s utilities all do nothing at all I think they’ve purged the back-end of older stuff so the programs that should download something and proceed simply wait forever.
If the download mode is not fastboot, is might be some sort of LG proprietary "fastboot" of sorts, maybe some research into this mode can help
Maybe this?
https://xdaforums.com/t/guide-lg-v20-back-to-life-download-mode-lg-flash-tool-unknown-model-in-lgup.3827732/
I’ll see if it can help me. Thank you!!! I appreciate your effort.