Hello there,
If you want sconfig to work the following 2 registry keys must exist otherwise it will show only "Custom"
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU
Create the keys and leave them empty with just default values, then sconfig will work and it will write values in the keys based on what you configure it to do.
Similar discussion here https://social.technet.microsoft.com/Forums/en-US/e07692a8-a8e0-49c6-bfc7-697d2e494a94/server-2016-not-accepting-quotmanualquot-windows-update-mode-in-sconfig?forum=ws2016
https://learn.microsoft.com/en-us/answers/questions/204828/sconfig-problem-settings-not-sticking
Hope this resolves your Query !!
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