Samsung Galaxy S4 (Network Unlock Request Unsuccessful) Troubleshooting
Follow these step carefully, as long as you have the correct code it will work 100% (Your phone must be updated to the latest firmware!)
1. Make sure that the phone PROMPTS for the code with a NON accepted sim card and that your IMEI is correct by dialing *#06#a. Go to the Dial pad and dial *#0011# b. Please click your MENU button (Bottom LEFT button) and click BACK on the menu that appears, Nothing will happen do not worry please move to the next step c. Please click your MENU button AGAIN and this time click KEY INPUT d. When the Key input box appears please input the number “1” and hit OK e. You will see a number 1 for a while, please wait until it changes into the SERVICE MENU f. Please click  UMTS >  DEBUGGING SCREEN >  Phone Control >  Network LOCK g. You will see 3 OPTIONS within Network LOCK h. Please click on number  Perso Sha256 INFO, the screen will change slightly i. Please hit the MENU button then when the menu pops up please carefully hit BACK to return to the previous screen j. Next Please click on number  Perso Sha256 ON, the screen will change again to a one line message k. Restart the phone on the screen by holding the power button and click RESTART l. When the phone prompts for the unlock code simply enter the unlock code provided to you m. Your phone is now permanently unlocked!