From zdnet.com
Windows 10 users are reporting that a second Windows update included in this month’s Patch Tuesday is causing problems.
According to reports, a bug in the KB4532693 update is hiding user profiles and their respective data on some Windows 10 systems.
Issues with KB4532693 have been reported on Microsoft forums [1, 2, 3, 4], Twitter, Reddit, and tech support sites like AskWoody, Bleeping Computer, and BornCity.