Missing photos on my iPhone I have a Macbook Pro and an iPhone that share the same iCloud account. On my Macbook's Photos I have a smart album that contains 52 photos. On the iPhone the album contains 40, with 12 photos are missing. 

How can I resync the missing 12 photos with the iPhone?
Smart Albums are not fully supported yet. See https://support.apple.com/en-us/HT204478

I would suggest trying to create a new smart album, perhaps with slightly different parameters, and see if you can work around the bug. Or, worst case, you could create a regular album.