Great, I tried to open the original catalogue (was backed up this morning) in LR5.4 and the same problem. All folders have question marks, no thumbnails at all.
Oh man, eight years of cataloguing kaput?
With the external drive attached and seen by OS X open LR CC and then go to File > Open Catalog. When the Finder dialog box comes up browse to the location of your LR 5 Catalog file and highlight it, click the Open button (or whatever it is called on a Mac). LR will need to close then reopen to load this other catalog. LR will then ask if you want to Upgrade this catalog to work with LR 6/CC 2015. Click the Yes button. If there is an Option to Name it do that with a name that is descriptive that it is a LR CC/6 catalog and if need be give it a number like 2 or New in the file name.
Once that is done do all your images show up and are reported as present (Not Missing)?
Exactly how is the external drive formatted? If in the Windows NTFS format then you have a utility loaded that allows OS X to Write to that drive (OS X can't natively write to NTFS formatted drives).
Open Finder and Browse that drive. Does it even show in Finder?
Check the permissions on that drive.
No, the exact same problem.
I even dug up a Jan. 17 backup from my second backup HDD (I have two backup HDD's) and attempted to run that in the original LR 5.7.1 (not 5.4 my mistake) and the exact same thing happens. All correct folder layouts are there, but all have question marks. All photo files have exclamation marks, no thumbnails, keywords are intact.
This shouldn't be causing anything but I have my main working LR Catalogue and previews on an external SSD due to my smallish 256Gb internal SSD. That has never been an issue, very fast.
Your assistance is very much appreciated by the way!
All of my ext. HDD's are formatted in Mac OS Extended (Journaled). I've always used that format.
In Finder do the external drives show up? Just checking.
In LR when you have folders with question marks right click on one of them and select Update Folder Location. See if you can browse to that drive and folder the images are store in. Select it and Yes or OK and see if that folder now doesn't have the question mark.
Oddly, after about 6 or 7 tries it worked. I have no idea what was preventing my system from acknowledging the main folder (with numerous sub folders inside) existed.
Thank you very much. You have no idea the relief that I am feeling now.
It is OS X. It some times take a while for external drives to show and be accessible. Hopefully this won't happen again.
Glad it got sorted out.