Re-booting following a power failure, I entered my pin & received a message something like, "Would you like to sign out? If you continue you risk losing personal data. You can protect your data by signing out, then signing in again". So I signed out, then signed in again and the boot proceeded but it was like a brand new installation. Desktop background was Windows blue, about half my desktop icons gone, all default apps reset, in Firefox all my plug-ins/extensions gone, all my bookmarks gone. And Windows Settings now won't let me set Firefox as the default browser and when FF offers to set itself as the default browser, that doesn't work either.

I've got the feeling this is some kind of identity issue gone awry but I don't know how to fix it. Hoping someone on this forum recognizes the problem, and knows a solution. Thanks for any help offered.