Importing photos from old Photos libraries to new System Photos Library

If you can open the libraries in question in Photos, check them for legacy media files. Very old libraries may contain videos or image files with a codec, that can no longer read by Photos 7.

• Check, it library contains items that appear in a smart album with "Photo is unable to upload to iCloud Photos". Items in the album may need removing from the library and converting to a new format.
• Make a test with exporting manually and reimporting into a new, empty library. Export in small batches to a folder on your external volume (with File > Export > Export unmodified Original". Then reimport to a test library. Items that cannot be reimported, will need converting to a more compatible format.

Or try it this way: How to Weed out Legacy Media in Photos for Mac - Apple Community

Me too! I am trying to merge a couple of large (25k - 35k) photo libraries, and I waited for Photos v7 because of its improved import function - you can now review for import and avoid too many duplicate photos - but I keep seeing this message. The message is wrong; I have repaired all my libraries - they can each be individually opened and edited. But the message keeps appearing, and I can't proceed.

Any help is appreciated.

Where is the old Photos Library stored? If it is on an external volume, make sure the external volume is suitable for a Photos Library. It should be prepared as described here, or problems with the file ownership and file system format may be making it impossible to repair the library: Move your Photos library to save space on your Mac - Apple Support

I used the Export Photos feature, retaining the metadata. With 33k photos it took a while. What's great is the ability in Photos v7 to selectively import "new" photos (non duplicates).

Yes, I've checked all that. Same message even when the libraries are sitting side by side in the same SSD with correct permissions and loads of space. As I noted I can open, edit and save each library with no errors, I just can't import one into the other.

What is the format of the SSD? Is the "ignore ownership" box checked?

Same here. I migrated and then repaired an old photo library and get the same message you see.

Have you read the messsage above by Leonie?

Thanks, that was very helpful. I don't use iCloud, but the way I found the outdated images was to export the library; that identified a dozen or so photos that couldn't be exported.