Hi, I am using Lightroom 5 and Mac OS X Capitan ver.10.11. I did imported images from external HDD to lightroom before and it working fine. But yesterday, I did add an folder at lightroom (left side from the main screen of lightroom) and I found that all my images "Preview unavailable for this file" and when I tried to re-import the images again, it shown "some import operations were not performed". Could you please assist on this issue? Thanks!
In the Import dialog, make sure the Destination panel contains all the right data.
On your external drive, make sure you have READ and WRITE access to the folders.