Standard Android commands sometimes fail on Oppo’s proprietary layer.
The error essentially means there is a security mismatch between the unlock token (or command) you are sending and what the device’s hardware expects. Why Does This Error Occur? the serial is not match fastboot unlock verify fail oppo
If you have tried all the above and the error persists, it is likely that Oppo has patched the exploit for your specific firmware version. In this case, you may need to wait for a newer version of the Deep Testing tool or a community-made exploit. " the serial verification will fail.
If your PC sees the device as a "Marshall London Bootloader" or a generic "Android Device," the serial verification will fail. the serial is not match fastboot unlock verify fail oppo