Microsoft has updated the support bulletin for the Windows 10 KB4556799 cumulative update to say they are investigating reports of issues. Windows users have been reporting that they are experiencing issues installing the latest update or having problems after it is installed. Microsoft is stating that they do not see widespread issues based on telemetry and customer feedback channels. Windows 10 2004 is expected to be released next week, so be prepared for a new round of reports of problems when people install the next feature update is released.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-is-investigating-issues-in-latest-windows-10-update/