If you have enabled the iCloud Photos Library on your iPhone, then are not all original images on your device. What you see in the iDevice Manager are thumbnails only, like on your iPhone. A transfer of images which are in the iCloud, is impossible. You have to disable the iCloud Photos Library in the iPhone settings.
The transfer back from iCloud to your iPhone takes couple of hours, depend on the load (use / hibernation) on your iPhone and the WiFi and internet connection speed.