However Mac Photos is only showing 11,535 for this total and when I look at Preferences/iCloud in Photos it says that it's uploading 12,231 items! Could this have caused a problem with Photos? I used Recovery to reinstall Sierra and this sorted that particular problem out. Why are the missing January 2017 photos not appearing in Photos on my Mac, and why is it apparently trying to upload 12,231 items? I should mention that I had a problem with Mail and also Safari (but not Firefox) on my Mac where the content of mail messages and web pages didn't appear at all. This figure agrees what the corresponding ones in both my iPhone and iPad. That library shows that there are some 11,542 photos and videos stored there.

I took some 8 photos this year on my iPhone and I was looking for them on my Mac but they're not there in Photos but they are stored OK in the iCloud photo library.

I have my Mac set to upload photos to my iCloud photo library and don't have my Mac storage optimised as I have plenty of storage space.

Photos of back of 2017 mac mini