Images not imported

OK. Some interesting results there....

I created a new account called 'vanilla' and used it to access the problematic photos library, Photos_WJ. It seems to be relevant that it is on a virtual disk called Test_WJ, on my desktop — the one for my own account, which is on iCloud. I accessed it from vanilla by using admin privileges to grant access to vanilla.

1. The result when logged in as 'vanilla' is that the photos library Photos_WJ in Test_WJ has the same problem: it still cannot import images — neither from Test_WJ/IMPORTS nor from vanilla's downloads folder (I downloaded a few random images from the internet).
2. If I create a new photos library TEST1 on the virtual disk, I have the same problem. It cannot import from either Test_WJ/IMPORTS or downloads.
3. If, however, I create a new photos library in vanilla's Pictures folder, it is fine. It can import from both Test_WJ/IMPORTS and downloads.

I conclude that the location of the photos library on the virtual disk is triggering the problem. Thre seems to be nothing wrong with the content or location of the images. I don't know why this should be the case - it has worked for years until recently. I created the virtual disk partly because putting the photoslibrary in an iCloud folder (including desktop) used to cause problems due, I understand, to the way packages are synchronised in iCloud. Maybe that is no longer the case? I also created the virtual disk to use extra encryption.

I also tried Safe Mode, but that made no difference.

I am not using this photos library with iCloud; it is not the System Photos Library. (I am having problems with the System Library too, but i posted that as a separate thread).

1. There are about 30 images all in JPEG format with .jpg extension. (I tried changing one to jpeg, but that makes no difference).
2. If I do File -> Import and select of all of them in the finder, they all appear correctly for review. If I then select one, or several, or all of them for import, nothing happens. Nothing is imported and there is no error message.
3. If I do File -> Import and select only one in the finder, it gives me the error message that the format is invalid.
4. If I drag and drop one or more, or all the photos I get the same error message.
5. If I create a new photoslibrary (called TEMP), I can import the pictures with no problem.

The virtual disk did not originate in iCloud, but is synchronised by iCloud because I ticked the 'desktop' option. But be clear, it is the .dmg file, not the Photos libray, that is on the desktop precisely because I know iCloud can break packages, so that is not the problem.

You double click the .dmg file to mount the disk, type in the decryption key and then it appears as an external 1Gb drive. Where is it safe... does not mention this specifically, but I assume the same rules as an external drive apply? The solution has the added benefit that the drive itself (i.e. the .dmg file) is mirrored to my other computers. I know it always syncs the whole .dmg file because after any change to it, iCloud reports that it is uploading 1Gb, the size of the virtual disk.

Where is it safe... says 'Do not format the external drive for the Photos Library as case-sensitive, if the internal drive is not case-sensitive'. The .dmg file is formatted as Mac OS Extended (Case-sensitive, Journaled) and the internal drive is formatted APFS, which is case sensitive, so this should be OK?

It is not read-only

It is not used for Time Machine.

This solution has been working for many years until the recent import problem. The existing pictures and folders seem OK.

I still think you are confusing the Photos package with the external drive (.dmg). No changes from iCloud can 'come in' to the mounted drive. If you update on two machines at a time, you are asked next time you mount the drive which version you want.

I use online photo sync for the System library. There is, sadly, no way of adding any other library for synchronisation.

I repeat that my solution has worked for years and still works for everything except import. Something must have changed recently to stop the import working.