Brief Description
This because ' .NCH file instead of .BAT file for BIOS' in recent board with AMI-UEFI BIOS support UEFI-shell mode, so legacy DOS-mode will not support this access and we strongly recommend to use 'BIOS update under UEFI-mode' as similar.
Solution
1. Enabled UEFI under BOOT in BIOS.
2. Ensure selected UEFI-Bootable DOS-disk with need BIOS folder files, mainly UEFI folder.
3. Type command “ fs0: ” or 'fs1:' , etc.
4. Locate target BIOS folder files.
5. Execute command “ go ” as standard method.
6. Wait for till flash complete without interruption.