Windows does not offer a driver installation from the updates. Also the manual installation lead to this result:
I also had many problems with fastboot. I read that the PC can be the problem. I tried all USB ports and sometimes it worked. Since I installed all Qualcomm drivers via Windows Update -> optional updates it works without problems. Try the Qualcomm usb driver.Windows does not offer a driver installation from the updates. Also the manual installation lead to this result:
--> devices boots into androidone screen and stuck
View attachment 5356379
View attachment 5356381
I used these drivers also:
They show a date from 2014 instead of 201615 seconds ADB Installer v1.4.3 ADB, Fastboot and Drivers What is this? This is All-in-One installer for 3 most needed PC tools for Android. No need to download big SDK for 3 small things. I originaly made it for my Kurdish friend AnGrY DuDe in...forum.xda-developers.com
None of it worked.
The linked drivers resulted in
I could solve it with a usb 2.0 hub
fastboot flashing lock
fastboot flashing lock_critical
Did you use the right DDV file?
Maybe that's the reason it's not installing. But I changed my phone's active partition to that which had April update, it still would not flash. Maybe we'll have to wait for updated bootloader unlocker.