Windows updates released this month are causing some GOV.UK sites to become unreachable in Microsoft Edge and Internet Explorer 11. This is due to the GOVUK TLD being added to Microsoft’s HSTS preload list. This means that Microsoft Edge will only connect to a G.UK site via HTTPS. Microsoft is aware of the problem and has updated the support articles for these Windows updates to state that they are working on a fix. For Windows 10 users, the ability to disable HSTs has been removed and users will have to wait for Microsoft to issue a fix.
Source: https://www.bleepingcomputer.com/news/microsoft/some-govuk-sites-unreachable-due-to-hsts-changes-in-windows-updates/