As I already mentioned a week or two ago, there's unlock key in TA Misc after BL unlock.
This file removes the key, therefore relocks the bootloader.
Flash with FlashTool.
DRM can't be restored!
Feel free to donate if this helped you
If you unlocked your phone with SEtool/Omnius - any testpoint unlock solution - YOU CAN NOT RELOCK BOOTLOADER! IT'S PATCHED SO IT APPEARS LOCKED TO SE, BUT ACCEPTS UNSIGNED IMAGES VIA FASTBOOT! SO STOP ASKING ABOUT IT, AND STOP TRYING.
Also, there seems to be problem with Verizon Plays, usually this doesn't work for them, when unlocked via fastboot.