Try right-clicking on a folder that contains images and choosing: Import Media
The folders that had images in them a few days ago now are empty. I tried right-clicking on the empty folders but the only options are: Reveal in Explorer, Add to Watch Folder, Rename, and Delete. I wonder what happened - why are my folders all empty except two.of them?
You must have moved files outside of Organizer using Explorer or Finder.
Try using File >> Reconnect >> All Missing Files
File >> Get Photos & Videos >> From Files & Folders
Then navigate to the new location.