If your device successfully transitions from the bootloader to Recovery Mode (often indicated by an Android robot icon or a different text menu), clearing cached system data can resolve startup blockages caused by corrupted update files.
If a hard reset doesn't work, try booting into recovery mode and performing a factory reset: blackberry keyone stuck in bootloader menu
If all else fails, you may need to re-flash the device's firmware. Note that this . If your device successfully transitions from the bootloader