Failed -remote 39-flashing Lock Flag Is Locked. Please Unlock It First 39--

For embedded systems only: , including disconnecting the main power supply, can clear the volatile state of the flash chip and sometimes release a lock that was set by a previous buggy operation. For Android devices, this means performing a full power-off (not a restart) and leaving it off for 30 seconds before booting directly into the bootloader again.

The error indicates a failure in the communication between your debugger (e.g., ST-Link) and the microcontroller. Specifically, the microcontroller's internal logic has flagged that the memory is restricted.

The error is politely telling you exactly what to do: before attempting any write operations.

Use this command if you are dealing with legacy Android architectures. Command C (Critical Partitions) fastboot flashing unlock_critical Use code with caution.

You cannot unlock the bootloader through a computer alone; you must first give the phone permission from within the Android OS. Open > About Phone . For embedded systems only: , including disconnecting the

When attempting to modify an Android device's firmware, run custom ROM scripts, or flash individual partition images, encountering the error means your device's bootloader security mechanism is actively blocking any unauthorized modifications .

A very common mistake is being in the wrong boot mode. If you see the unlock_bootloader partition size reported as 0 , you are likely in "fastbootd" (userspace fastboot) rather than the bootloader itself.

Once in bootloader mode, use one of the following commands depending on your device: fastboot flashing unlock (Standard for newer devices). fastboot oem unlock (Common for older devices). Confirm on Device

Connect your device in bootloader/fastboot mode and run: set it to Disabled .

Yes. The bootloader unlock process will wipe all user data from your device, including apps, photos, and settings. It performs a factory reset to protect your personal information. Back up everything before you begin [6†L22-L23][8†L12-L13].

The error will manifest in your command-line or terminal interface after issuing a fastboot flash command. It will appear in a similar format to: FAILED (remote: 'Flashing Lock Flag is locked. Please unlock it first!') [5†L13-L14][7†L20-L21]. While the text is a clear indicator, you might also see other variations referencing lock states, such as flashing is not allowed in lock state [8†L8-L9].

If the toggle is unclickable, connect to Wi-Fi. If it stays grey, your carrier may have permanently locked the bootloader (common with Verizon or AT&T models).

: Connect your device to the computer and run: adb reboot bootloader Once in bootloader mode

Connect your phone to your PC and run: adb reboot bootloader

: If you are trying to flash low-level files like the bootloader itself, you may also need to run: fastboot flashing unlock_critical Important Troubleshooting

Go back to the "Erasing & Programming" tab and click "Full Chip Erase" . This usually removes write protections. 2. Using ST-Link Utility If you are using the older STM32 ST-Link Utility: Open ST-Link Utility. Go to Target -> Option Bytes . In the Read Out Protection section, set it to Disabled . Click Apply . 3. Using OpenOCD (Command Line) If you are working in a Linux environment or using OpenOCD: