[Xiaomi Mi 5 Guides, News, & Discussion] stefipant:
Hi, I run into the same issue on win 10 and also installed the android sdk to get the drivers.

Device Mi5 Pro

Latest chinese dev 6.10.20 (MIUI8)

I can find the device with fastboot, however "fastboot getvars" fail all the times with the same error:

fastboot getvar all
getvar:all FAILED (command write failed (Unknown error))

Thus the mi unlocker tool runs into the same issues:

DEBUG <11:15:16.127,T:5796> : Initializing native downloader...
INFO <11:15:16.127,T:5796> : init resource C:\Users\ose\Downloads\MiFlashUnlock_1.1.0317.1_en\res\ language:en region:
ERROR <11:15:17.003,T:2000> : product: return:getvar:product FAILED (command write failed (Unknown error))
ERROR <11:15:17.648,T:2000> : soc-id: return:getvar:soc-id FAILED (command write failed (Unknown error))
ERROR <11:15:18.294,T:2000> : soc_id: return:getvar:soc_id FAILED (command write failed (Unknown error))
ERROR <11:15:18.993,T:2000> : board_version: return:getvar:board_version FAILED (command write failed (Unknown error))
ERROR <11:15:18.993,T:2000> : Can't identify device in fastboot mode.(num=0)
INFO <11:15:34.057,T:4264> : to login by name:XXX pwd:XXX sid:XXX verify:EMPTY sec_token:EMPTY
INFO <11:15:34.090,T:4264> : LoginStep1
DEBUG <11:15:37.791,T:4264> : OnAccountLoggedIn
DEBUG <11:15:43.173,T:4264> : OnNewServiceCookies
DEBUG <11:15:43.173,T:4264> : Login success and get user detail
INFO <11:15:49.223,T:2032> : status result: {
"applyStatus" : 2,
"code" : 0,
"description" : null,
"shouldApply" : true,
"uid" : 1554152998
}
DEBUG <11:15:49.223,T:2032> : unlock status: 2
DEBUG <11:15:49.223,T:2032> : should apply:true
INFO <11:15:53.357,T:5796> : connected
DEBUG <11:15:56.569,T:10612> : VerifyDeviceInfo
ERROR <11:15:57.230,T:10612> : product: return:getvar:product FAILED (command write failed (Unknown error))
ERROR <11:15:57.873,T:10612> : soc-id: return:getvar:soc-id FAILED (command write failed (Unknown error))
ERROR <11:15:58.516,T:10612> : soc_id: return:getvar:soc_id FAILED (command write failed (Unknown error))
ERROR <11:15:59.215,T:10612> : board_version: return:getvar:board_version FAILED (command write failed (Unknown error))
ERROR <11:15:59.215,T:10612> : Can't identify device in fastboot mode.(num=0)
WARNING<11:15:59.215,T:10612> : cannot get product info again
ERROR <11:18:15.927,T:2000> : product: return:getvar:product FAILED (command write failed (Unknown error))
ERROR <11:18:16.589,T:2000> : soc-id: return:getvar:soc-id FAILED (command write failed (Unknown error))
ERROR <11:18:17.233,T:2000> : soc_id: return:getvar:soc_id FAILED (command write failed (Unknown error))
ERROR <11:18:17.935,T:2000> : board_version: return:getvar:board_version FAILED (command write failed (Unknown error))
ERROR <11:18:17.936,T:2000> : Can't identify device in fastboot mode.(num=0)
ERROR <11:18:19.035,T:2000> : product: return:getvar:product FAILED (command write failed (Unknown error))
ERROR <11:18:19.677,T:2000> : soc-id: return:getvar:soc-id FAILED (command write failed (Unknown error))
ERROR <11:18:20.319,T:2000> : soc_id: return:getvar:soc_id FAILED (command write failed (Unknown error))
ERROR <11:18:21.025,T:2000> : board_version: return:getvar:board_version FAILED (command write failed (Unknown error))
ERROR <11:18:21.025,T:2000> : Can't identify device in fastboot mode.(num=0)

I also cannot go back to a Global stable/dev rom, using the updater.

Any advises?