Cocoa error -1 in Photos

Well, without the answers to some of the questions above I'm going to be guessing a little. But you have one huge advantage. If all your photos are in iCloud, you can easily recover your full library from there:

The easiest way is to create a new empty library on your mac, (in the pictures folder is the normal place). Set this new library as the system library, and make sure iCloud photos is enabled, and your mac will then download everything from iCloud photos library into your newly created library.

First do you have enough space on your mac for your full library to be downloaded again. If so, carry on - if not, take a backup of your current library and then delete it from your mac. ( You still have the previous version on your old Mac, don't you?)

Then:

Hold down the option key while starting photos, and click "create new". Name it Photos Library.photoslibrary, and locate it in your pictures folder. (First screenshot).

Then open the new library - go into photos preferences (general tab), and click "use as system photos library" (second screenshot)

Finally in photos preferences iCloud tab, set it up as the final screenshot. (You need to have enough space on your mac to download all the photos from iCloud)

It will then download everything from iCloud to the new library.

Main issue I see - NAS Drives are not suitable locations for external storage of a Photos library. All sorts of problems can result, including the sorts of errors you are seeing.

An external drive must be formatted APFS or MacOS extended (journaled) (preferred for spinning drives)

It Must not be (or have been) used for time machine.

It must have the 'ignore ownership" checkbox ticked.

It should not be on a memory stick, SD or similar.

It must also not be a network drive (a direct connection is required - eg USB or Thunderbolt).

File sharing services such as iCloud Drive, Drop box, Onedrive etc are not compatible with Photos libraries.

It stands to reason that if you want any sort of reasonable performance it should be a fast drive with a fast connection.

See

https://support.apple.com/en-gb/HT201517

Update ... and problem seemingly solved! I stumbled across this article and decided to give a restart of my iMac in Safe Mode a try:

https://discussions.apple.com/thread/251293841

When opening Photos in Safe Mode nothing happened, but after I had rebooted into normal mode, the shared folders have repopulated from the Cloud!

Will keep an eye on this, but for the moment this has solved the problem. Good luck, All.

That can mean damaged originals, or a damaged photo library. To help with diagnosis, can you answer the following:

• Has this just started for no apparent reason, or have you upgraded MacOS (if so from which version) or changed machine? or some other event?
• Where is the library stored (System drive or external drive)? If external - what is the format of the drive?
• Is the library on a network drive or in some sort of cloud storage (EG Dropbox or NAS)?
• Have you used any apps to remove duplicates, if so, which?
• Have you used any "clean up" or "speed up" apps
• Do you use Icloud to sync photos?
• If so, do you have optimise local storage set?
• Are your files imported into photos (photos preferences general) or left as referenced files?

Hi Tony,

I moved my Photos library to a NAS folder and it works fine when looking at the individual pictures, but shared albums are only partially populated, if at all. If I try to import an individual picture, I get Cocoa error -1., too. This problem occurs on my iMac only, Photos for iPhone works fine and displays all the shared albums as it should.

Any ideas? Many thanks for getting back to me...

Hi Tony,

Thanks for coming back to me/us. I misspoke earlier: the Photos library is not on a NAS, but a locally USB connected drive, an WD Thunderbolt Duo, which is formatted HFS+J, according to its utility app. It was never used for Time Machine.

Can you please advise on this? Many thanks!