Mac Photos - Unable to Upload x Items

Noticed the following message in Photos app on my Mac

Unable to Upload 2 Items

First question I had was ‘Why not?’ followed by the question ‘Which 2 photos?’

The answer on the first question will be ‘answered’ later, the answer on the second question is easy but not directly obvious.

Smart Album

To get an overview of the photos not uploaded to iCloud you need to create a Smart Album, like shown below

Smart Album Condition

For the photos involved only the thumbnail seemed to be in the library. Clicking the photo to view or edit just gave me a empty canvas. Also most of the metadata appears to be missing
Digging into the Package Contents of the Photos library I could not locate the photo’s within the Masters-folder, but was able to copy out the thumbnails from the Thumbnails-folder.

Checking the log files

Using the Console app I reviewed numerous log files, but have not been able to locate any Photos (or iCloud) messages relating to any issues. So no luck there.

Backup, backup, backup

Before going any further I created a backup of my complete Photos library onto an external drive. While copying the library the Finder gave me the following error message.
So there is something definitely something wrong with my Photos library. Interestingly enough the copying of the library did continue, but after the copy action had finished there was now Photos library on the external drive. So I guess the next step will be performed without a local backup (all photos, except the two, are stored in iCloud and have been uploaded to both Flickr and Backlaze).

Repairing the Photos library

To get the option to repair your Photos library you first have to Quit the Photos app. Next hold down the keys ⌘+⌥ and launch Photos app. The following message should appear. Click ‘Repair’ to start the repair process

Photos Repair Library

In the end the repair didn’t make any difference (since the Photos library only had the thumbnails). So in the end I deleted the two troublesome photos from the library and added the thumbnails as new photos to the library.