Not all pictures appear in apps
I believe that imported pictures aren't displayed in the "Media Inspector" > "Photos" tab > "iCloud "sidebar item…

In "iPhoto.app" > "Preferences" cmd , check if in the "iCloud" tab the followings are ticked :


"My Photo Stream"
"Automatic Import"




If so you might consider creating a "Smart Album" cmd alt ⌥ N
For example "iCloud Stream" that will match "all" the following conditions :




"Keyword" > "is" > "Photo Stream" ;


get last month (as for iCloud)


"Date" > "is in the last" > "1" > "Months" ;




In a "Media Inspector" you may know select your newly created smart album "iCloud Stream" :