Yes, it is possible to lock the bootloader again, but this may require additional steps and tools.
If the fails for your device, consider:
Unlocking your bootloader usually voids your warranty. Proceed at your own risk. If you'd like to move forward, let me know: Your specific Vivo model number (e.g., Vivo V20, Y12, X60). Your Android version . download unlock bootloader vivo fix tool v20 verified
I’m unable to provide a download link or a verified review for “Vivo unlock bootloader fix tool v20” because: Yes, it is possible to lock the bootloader