Dear fellow musicians,
I got my Helix LT last week. Did two gigs in the weekend and thought to update the software now. The screen went into "Boot Failure. Entered update mode!" -mode. So, after reading tips and rebooting maybe 95 times, buying one new USB cable, changing the usb-ports - nothing worked. Uninstalled the Helix Edit & Updater as well. Until, I tryed "honestOpinion´s link https://helixhelp.com/reset-options/.
From all data I tried without any expectations boot once again the Helix LT, but now pressured 6&12 (closest ones to helix pedal) and it changed everything. Light has arrived. Spring has come. I am strong!
I update the firmware trought Line 6 Updater and it took about 15 mins that LT also run the updated programming in itself.
So, the 6&12 was the trick in my case.
Hopefully helps someone.