Help please - 'Photos with unavailable original files cannot be opened.' - where are they?

It looks like you did not copy the photos into your Photos Library, when you imported them. Please check the preferences in Photos: Photos > Preferences > General. Is „importing: Copy items into the Library checked, as it should be? If this option has not been checked, your photos are not stored in the library and you must not delete the or move the photos you import to Photos. They are your only copies.

to find all photos with missing originals create a smart album:

• File > new smart album.
• Set the rule to „photo is referenced“

is this album empty? If not, select small batches of photos in this album and try to copy them into the library with File > Consolidate.

That is bad. It is as I expected and Photos did not copy the photos you imported into the Photos Library, because it has been set not to copy the images.

It is expecting the photos in exactly the same location where they have been, when you imported the photos.

Do you remember where the photos have been, when you imported them? Are they still there or did you delete them or move them elsewhere? When you airdrop the photos to Photos they probably arrived in the Downloads folder. Are they still there? What did you do with the airdropped photos after importing them to Photos?

Hi

In your situation, I would create a folder on the hard drive, and get all of the photos I want to put into the photos app into that folder.

Then when you have everything gathered together, you can use the file>import command in the photos app, and point it at that folder to import all images in one step. Now you have the "copy items to library" selected, they will all be copied into your photos library.

If you want to create a folder organisation below the top level folder, you can also replicate that in the photos app during import, using the "keep folder organisation" checkbox after clicking "review for import"

Finally once you have imported, and checked everything is as you want it, you can remove the source folder from your drive. I would archive it onto an external drive, as a backup first.