(Genius app name there, Apple
I have a folder of photos from a USB stick. I drag the folder onto Photos and wonder what's happened.
Delightfully, it shows them as thumbnails, asks where it should import to (including offering me to create a new album for this) and even offers to create a hierarchy based on the folders (which doesn't make sense in this case because it's just one flat folder, but it's the thought that counts?).
The album gets created. Then, nothing.
So I try instead dragging individual photos. Now all I get is:
Cannot Import Item
This item cannot be added to your Photo library because it may be in an unrecognisable* file format or the file may not contain valid data.
Then it lists the files, and every one with a Reason; in this case: "** Invalid: The operation couldn't be completed. (PHPhotosErrorDomain error -1.) **"
And that's where I'm stuck. Photos Version 5.0 (101.15.190) on 10.15. Maybe I should try a 10.15.1 beta?
*) Why are portions of macOS in British English now? Ugh.