Ryo.F 曰く、

一部環境で“Windows Update”に接続できない問題、原因は外部DNSサービスのダウンとデータ破損
Windows 10 and Windows Server 2019 update history

February 4, 2019 9:45 PM PST
“The Windows Update service was impacted by a data corruption issue in an external DNS service provider global outage on January 29, 2019. The issue was resolved on the same day and Windows Update is now operating normally, but a few customers have continued to report issues connecting to the Windows Update service. We expect these issues will go away as downstream DNS servers are updated with the corrected Windows Update DNS entries.”