Sunmi | V2 Unlock

It sounds like you’re asking about — likely a smart POS terminal or handheld Android device.

Advanced users looking to "Root" the device or install custom ROMs (like LineageOS) to turn the POS into a standard tablet will encounter the Bootloader lock. Sunmi devices generally come with locked bootloaders, and unlocking them is a complex process that can void warranties and brick the device. Sunmi V2 Unlock

This is the most common scenario. You have a used device, or an employee left the company without sharing the PIN. This is a standard Android security feature. While annoying, it is usually the easiest to resolve, though it involves data loss. It sounds like you’re asking about — likely

For advanced users only (voids warranty, security risks): Sunmi V2 Unlock