Pages disappeared

I wrote a course a few years ago and changed computers. I made a back up of my course. Now I open Scrivener and all the “folders” and pages show up on the left. But when I click on the page on the left it’s a blank page. How do I get those pages to show up again.

This happened once before and some on the forum was kind enough to do a live Zoom room with me and fixed it right away. I don’t know why it’s happening now. When I open Scrivener from the desktop the backup opens. I can’t find the original course.