Stacks no longer appear

I have many photos in many stacks in my catalog but the stacks no longer appear. The photos and associated metadata seem to be intact.

Evidently the problem arose when I rearranged folders on a couple of hard drives using windows file explorer.  The catalog is now on a different drive than the photos. One strange thing that happened was that, after opening a back-up catalog file to see if they had stacks (and found that they didn't),  I went back to open my latest catalog file that I had just closed, I got a message saying that the catalog needed to be updated.  Light room then took the Catalog, updated it, and added the suffix “-2”. 

When I tried to open a backup version that was made before I made any changes to the hard drives, it open showing the stacks and fuzzy thumbnails of the photographs (the photos were missing). It showed the photos with the stacks. Since the photos were missing, I found the photos in missing folders and imported them and then synced the folders.  I did that, all the correct photographs appeared but again there was no stacking. 

Any ideas?  Thanks.