There have been so many changes and additions to Windows 10, I can't keep track of them all. I ran into an issue with Microsoft Edge opening the startup tabs but not loading the pages and being completely unresponsive. After a quick search, I discovered Repair/Reset was added with the Windows 10 Fall Creators Update (version 1709) and it is easy to use.
  • Click Start (Windows icon) > the Settings icon and select Apps > Apps and Features.
  • Scroll down to Microsoft Edge & click it.
  • Select Advanced options.
  • Try Repair first and if that doesn't work, select Reset.

In my case, Repair didn't work but Reset did. The only thing I had to do after the repair was to re-activate the extensions.