: If your tool supports it, the command is usually: fastboot flashing unlock
: Nokia devices are notoriously difficult to recover from a "Hard Brick" if the bootloader or preloader is corrupted. Proceed only if you have the Stock Firmware (scatter file) ready for recovery. To help you specifically, could you tell me: Are you trying to an existing ROM or a new feature for one? Do you already have an unlocked bootloader specific feature nokia c1 custom rom