Bufot Code 28 is related to many factors, from my experience, if the firmware update tool does not recognize it, you can try these ways, if all do not work, the camera may be dead completely.
1 reinstall the driver to try.
https://www.yuque.com/zwopkb/hardware/flue0a?
2 Try 'Reset Windows Update Agent' tool to reset it to try.
3 Connect the camera to other computer which can recognize it to reflash the OS.