If flash firmware failed with RS-232 interface, please try below step to recover.
0. Do not turn on scanner power.
1. Run AutoHostV1_0.exe.
2. Choose the COM port what you connect.
3. Click "Search" to open the firmware file.
4. Press "Run" first.
5. then power on the scanner immediately.
6. The firmware would be updated in a while. After that, the unit will restart.
If can't be restored, please send it to back to repair through RMA process.