I recently bought a new iMac computer. Also downloaded Lightroom 6. In the past I have worked on a PC using Lightroom 5. I would like to transfer my catalog to my new computer (PC--> Mac; Lightroom 5 version---> Lightroom 6). I have copied all the program files (lrcat) to an external hard drive (Passport) along with the photos that belong to that catalog. When I open Lightroom 6 on my Mac and try to laugh with the catalog from external hard drive it is giving me this error message..." Lightroom cannot open the catalog named Lightroom 5 Catalog located on volume "My Passport" because Lightroom cannot save changes to this location. Lightroom Catalogs can not be opened on network volumes, removable storage or read only volumes." Does anyone know what that means and how to get this catalog to be recognized on my Mac?
Check the Write permission on your drive and the directories.