Starting in late January, Windows 10 users began reporting that when they tried to perform an update, Windows would state that it could not connect to the Windows Update service. At the time, Microsoft did not disclose the cause of the issue, but as users could fix the problem by changing their DNS servers, it was widely thought to be a DNS problem. Microsoft finally disclosed that this was a DNS issue that was caused by an outage at an external DNS provider, which caused corruption of DNS Data.
Source: https://www.bleepingcomputer.com/news/security/microsoft-states-windows-update-dns-issues-are-finally-fixed/