its not phone fault . it was driver . i have this problem before .
as i remember i install this driver USB Driver in Device Manager .
right click > Update Driver > Browse my Computer for driver .
or other alternative .
disable signature your windows using this
bcdedit -set loadoptions DISABLE_INTEGRITY_CHECKS
bcdedit -set TESTSIGNING ON
then restart
download MiFlashTool . if you got error when open MiFlashTool .
make new folder inside MiFlashTool folder with name Log .
then open MiFlashTool > install driver from there .
this is how i success fix fastboot issue .
as i remember i install this driver USB Driver in Device Manager .
right click > Update Driver > Browse my Computer for driver .
or other alternative .
disable signature your windows using this
bcdedit -set loadoptions DISABLE_INTEGRITY_CHECKS
bcdedit -set TESTSIGNING ON
then restart
download MiFlashTool . if you got error when open MiFlashTool .
make new folder inside MiFlashTool folder with name Log .
then open MiFlashTool > install driver from there .
this is how i success fix fastboot issue .