Nokia Lumia 520 with Lumia Denim.
I have three Windows Phones (all 8.1) and two of them back up photos to OneDrive, but one does not.
I have of course turned on this feature, and I only connect via WiFi (have disabled cellular data, same as on my other phones).
But the photos never backup to OneDrive, unless I manually share them with OneDrive.
Is there something I have missed to get this to work?