Photo import not working

ExFAT is a no-go for a Photos Library. You have been lucky that you did not have any problems previously. You definitely need to move the library to a correctly formatted volume. Here is a detailed guide how to format the external volume: Move your Photos library to save space on your Mac - Apple Support

if your external drive is large enough, you might try to create a second partition on the same drive, if you need the ExFAT drive to transfer documents and data to a windows computer.

Ok, j, you've got the pictures in a folder on your computer, but for some reason they don't import. First, use Disk Utility to make sure that the external drive is formatted as either APFS format or Mac OS Extended (Journaled). In newer versions, Photos is way more dependent on the format of the drive, and troubles may not show up immediately. And it's also important that, since formatting, Time Machine has not been on the drive. A Time Machine drive allows only Time Machine to be on it.

How are the pictures formatted? jpg, Raw, png, or what? Can you view an image in Finder by selecting it and pressing spacebar (Quickview)? Can you drag one of these contrary image files into Preview?

How are your Photos preferences set?

In Photos>Preferences>General:

Is "Use as System Photo Library" grayed out (indicating it is) or solid (indicating this isn't your system library)?

Is "Copy Item to the Photos Library" checked? (This is the default, indicating a "Managed Library")

In Photos>Preferences>iCloud:

Is "iCloud Photos" checked?

If it is, is "Optimize Mac Storage" checked?

Have you tried these things?

• Restart the computer (of course)
• Rebuild your Photos Library--close Photos and re-launch by option-command-clicking the app icon.
• Make a new user and see if the same problem recurs with it
• Use another library if you have one, or make a small test Library with a few pictures in it and see if the same thing happens.
• Start in Safe Mode (different for different computers) This bypasses certain potentially disruptive processes.

          Start up your Mac in safe mode - Apple Support 

One of these steps may fix the problem, but their failure to work is also diagnostic.

First thing that pops out is " library from an external hard drive." How is this drive formatted. For it to work with Photos, it must be formatted as "either APFS format or Mac OS Extended (Journaled) format." Also "You can't store your library on a storage device used for Time Machine backups." Nothing else will give complete functionality.

Can you read the SD card with Finder? Can you view an image in Finder by selecting it a pressing spacebar (Quickview)? If so, can you drag the image files from the SD card to a Finder folder, and then import from there?

Have you tried the app, "Image Capture" in the Applications folder? It is sometimes less finicky.

Richard.Taylor, I'm having the exact same problem as yourfriendpatrick. I did what you recommended and I can move the photos from the SD card to my computer but then when I attempt to import them into my library they never import and my import status stays at "0 of 94" for hours. My library is also on an external hard drive and it is properly formatted because I've used this drive with Photos for the past 7 years. This is the first time I've had import problems.

Ok, looks like my issue is the formatting. I checked the drive and it is formatted as ExFAT. I'm assuming the only way to fix this is to move my library off the hard drive, reformat the hard drive to APFS or Mac OS extended, and then move the library back. Let me know if there is a simpler way. Thanks for the help!

I'm surprised it's worked all these years without being in one of the preferred formats.