Root HELP: Unbrick and then update SGH-i527

[lioness818]

My phone was previously rooted (can't remember if I used mobogenie or Kingoroot). I un-rooted using superuser in an attempt to get the update to 4.4. when I tried to boot in recovery mode it says "System software not authorized by AT&T has been found on your phone. Please turn off your phone and go to the nearest ATT store for help" and "Secure Fail: KERNEL". It can be put in download mode. I've tried using odin to go back to the stock rom but get a "fail" everytime (with the pit file and without) and the message "Complete(Write) operation failed". I also tried to push files using fastboot but the computer doesn't recognize my device when I type "adb devices" -- nothing comes up. I also tried Kies but it just keeps saying "connecting" but never does.

Ultimately what I am trying to achieve is #1 unbrick the phone (of course) and #2 to end up with at least 4.4 (or possibly higher if available).

 

[Carlo Lita]

Intall twrp through odin. 'diable auto reboot!'
after flash you see 'pass'. remove cable and force shutdown by removing battery for 5sec replace then reboot to recovery by holding vol+, home and power button then release power button when factory logo apear. now you can install aosp or RR roms Android 6 or 7.1