So I've got a folder of photos. And when I want to synchronize the folder, it says there's photos that are missing and that it'll remove them from the catalog. But the photos it says are missing are on the drive, and there's no question mark on the files and everything is working fine. It just wants to randomly remove photos from my catalog when nothing is wrong with them...
On the drive and in the same folder they were originally in when they were imported is 2 totally different things.
I've been using LR for 10 years with the same catalog I started with in LR V1 and have never had this happen.
Right click on one of those images and select Show In Explorer or Finder (depending on the OS your computer is running. Does it take you to the folder you are trying to synchronize?