The Serial — Is Not Match Fastboot Unlock Verify Fail Oppo !!better!!

If successful, the error will disappear, and the bootloader will unlock.

In other words, your phone knows its unique serial number (or IMEI). It compares that number against an internal allow-list. Unless you have applied and been approved for an unlock token via Oppo’s official "Deep Testing" app, the serial number check will fail every time.