jpg photos recognized on one Mac but not another

CaptRog wrote: I have a bunch of older jpg photos in the Photos app that I am trying to transfer (via usb thumb drive) to my wife's Mac.

How are you transferring them out of Photos? The best way would be to use "File>Export>Export Unmodified Originals," or to use "File>Export>Export nn Photos" for edited pictures. "Export" should produce compatible files, though other methods may not.

If they don't work after you have used the Export process, then Yer_Man's suggestion may fix it. If that doesn't work, try using Export from Preview.

Have the problematic JPEGs edited with an external editor?

Sometimes external editors are saving the edited versions backt to Photos with the filename extension "JPG", but they are not JPEGs at all, but camouflaged TIFFs and Photos will refuse to import them.

Have you checked the Info for the problematic files in Preview, when you viewed it in Preview? Just open the Info in Preview with ⌘I and look at the "Kind". Does it show JPEG or something else?

For example, this TIFF has been saved back to Photos by Luminar, with the filename extension JPG, but it is a TIFF file, as shown in Preview.

As a test launch Photos with the Option key held down and create a new, test library.  Try to import some of the problem photos to see if the same problem persists. Does it? This tells us if the problem is limited to your current library or is more wide spread.

It they import successfully close the test library, open your original library and try importing again.

Can you open these particulate files on her machine with Preview?

If so, save them. nothing else and then try import them.

First, before you mess around with the Library too much, make sure you have a backup.

Next, try rebuilding your Libraries database by closing Photos and re-launching by

option-command-double-clicking the app icon. It may take awhile.