You may need to enable "OEM Unlocking" again after a major OS update. Re-check Developer options.
: Unlocking the bootloader using this tool will erase all user data and may disable certain high-security features like "Find device". It is recommended to download the software only from authorized platforms like the official Xiaomi Unlock Page .
Xiaomi implemented Anti-Rollback protection on many devices starting around 2018. This is a safety measure that prevents users from flashing older firmware or using older tools on newer phones. Attempting to use a 2017 unlocking tool on a phone with ARB active could result in a , rendering the device permanently unusable.
Use 7.6.727.43 if you own a device launched between 2018–2020. For Xiaomi 12, 13, or newer, use the latest version from the official website.