Hi, I have had this phone for three years now, with little or no issues. Then, suddenly it stopped booting up past the LG screen with the words "Security Issue" under the LG symbol. I tried the hard reset button combo to get to the reset screen (Vol down + Home + Power key), but received this message at the top of the LG screen:

[1110] boot certification verify
[1110]Secure booting Error!
[1110]Cause : boot certification verify

And it would vibrate twice every time I started the phone with the above message.

I'm interested in fixing this as more of a challenge thing, than a need. A few more bits of info...
The phone was never rooted. And it was working perfectly before this problem. Thank you for any info on this.✌😊