Lenovo A916 cannot unlock bootloader
Try these commands:


adb reboot bootloader


Wait for your PC to install fastboot drivers for the device then


Check if device is detecting in fastboot mode

fastboot devices
If device is detected use the following command to unlock bootloader:

fastboot oem unlock


Follow the screen instructions and after unlocking reboot the device using the command:

fastboot reboot

Hope It will work for you.

Note: Unlocking bootloader will erase entire data.