https://www.techradar.com/news/new-patch-for-windows-10-april-2018-update-appears-to-break-some-pcs

Microsoft has recently released a cumulative update, titled KB4103721 Version 1803, which was aimed at fixing a number of bugs discovered in the Windows 10 April 2018 Update, but it looks like it is also causing problems of its own for some PCs.

A thread on Microsoft’s Community support forum features a number of people who have had trouble turning on their PCs and booting into Windows 10 after installing the patch, and instead being faced with a black screen.