The error message "FAILED (remote: 39: flashing lock flag is locked. Please unlock it first)"
Step 2 – Look for a physical lock lever
Some large copiers have a transport lock for the drum/fuser unit. Unlock it if present. The error message "FAILED (remote: 39: flashing lock
Alternatively, power off the device and hold Power + Volume Down until the Fastboot logo (often a mascot or text) appears. 3. Unlock the Bootloader Obtain the Unlock Code/Token: fastboot devices
Here’s a clear, helpful explanation of that error message, broken down for users or support documentation. helpful explanation of that error message
Legacy/OEM Unlock: If that fails, some older or specific devices use:fastboot oem unlock
fastboot devices