I just bought a new MacBook, copied over the Pictures folder (including Lightroom), installed Lightroom CC (release 8.0; build 1193777 -- exact same release as on my old MacBook) and launched LR. LR displayed a message that it was upgrading "Lightroom Catalog-2" to "Lightroom Catalog-3" and then all hell broke loose. Most (but not all) of everything is gone or corrupted. Folders deleted long ago show up, new folders don't show up. Metadata (e.g titles and captions) are gone. Most (again, but not all) of the Develop module changes (crop, tone, etc.) are gone. I can't be the first to experience this so any help will be most appreciated. I tried Adobe Support chat but gave up after 30 minutes.
My first thought is that you opened an old catalog. Having to upgrade the catalog and changes in folders would indicate this.
In Lightroom, go Menu > File > Open Recent...to see the Catalogs that Lightroom can find.
Or, Search your computer with Mac Finder for all .LRCAT catalog files to find your current working catalog.
Thanks. I only had one catalog (Lightroom Catalog-2.lrcat) but now have two since Lightroom "automagically" created "Lightroom Catalog-3.lrcat" when I first launched it on my new MacBook. When I force LR to open LC-2.lrcat, everything seems to be OK. LR seems to have gone off the deep end when creating LC-3.lrcat.