: Ensure the Wipe Data (Userdata) and Wipe Cache options are selected to ensure the lock is actually removed.

The Sony Xperia ZL (designated by the model number e6833 for the LTE variant) represents an era of Android hardware where manufacturer-imposed security mechanisms were robust yet contained exploitable service pathways. The "bootloader lock" is a digital signature verification mechanism enforced by the primary bootloader, preventing the execution of any operating system kernel or recovery image that has not been signed by the manufacturer's private key.

Download the correct firmware, specifically for your variant/region. Drivers: Sony USB Drivers and Fastboot/ADB drivers. Step-by-Step Guide: Flashing FTF to Remove Lock