What should I do if win10 upgrades 9789 fails?

First, users are advised to restore the registry key values ​​that have been changed, then restart the computer, and then try to upgrade again when the network is stable. This method is invalid. You can refer to the following methods.
Method 1: Rename the SoftwareDistribution folder

· Disable the Windows Update service in the service
· Open the C:Windows folder and right click on the SoftwareDistribution folder to rename it.
· Re-enable the Windows Update service after the rename is complete.
Method 2: Repair Windows components

Simultaneously press Win + X, select command prompt (admin), and then enter the following command (you can also copy and paste right):
Dism /Online /Cleanup-Image /CheckHealth
Dism /Online /Cleanup-Image /RestoreHealth
Method 3: Use the ISO image to upgrade directly to Win10 Preview Build 9879