All of my catalogs are on an external drive. I updated through Adobe Cloud, PS, and I thought LR, but I don't see that update in my history. I also updated my OS to El Capitan. Now, when I open LR, I get the message that catalogs cannot be stored on external drives, etc when I try to open a catalog that I was able to open just a couple of hours ago. I am in the process of downloading 10.9 to replace 10.10 (which I just installed.)
Any help is greatly appreciated.
We would need to see the exact wording of the error message you are getting.
Mac OS upgrades seem to like to mess with file and folder permissions.
Using Finder, go to your folder containing the catalog, and verify that you have READ and WRITE access to that folder and its files.
I discovered what was going on. After hooking up a different external drive, in the attempt to open a catalog, I discovered that it worked (on that different drive.) So I went back in and looked at permissions for the drive where I was unable to open the catalog. What I discovered was that the Seagate Backup Plus drive that I was using, had its permissions taken away. I was able to "read" only.
I then found a patch for it and after running the patch, I haven't had any problems. LR is working as it had before. I guess that incompatibility was the reason for LR giving the message.