System and user certificates might be lost when updating a device from Windows 10, version 1809 or later to a later version of Windows 10. Devices will only be impacted if they have already installed any Latest cumulative update (LCU) released September 16, 2020 or later. Devices using Windows Update for Business or that connect directly to Windows Update are not impacted. This might also happen when using outdated physical media or ISO images that do not have the latest updates. We are working on a resolution and will provide updated bundles and refreshed media in the coming weeks.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-cumulative-update-preview-kb4601382-released/