This problem can occur when the iPhone does not allow the app to access photos.
Set the iPhone/iPad/iPod touch to allow PCS Manager to access photos.
If copying of a large number of files to the Camera Roll fails, reduce the number of selected files, then try again.
If the format is not supported by the Camera Roll, the file cannot be copied to it. For information about the file formats that can be copied to the Camera Roll, see the operation manual of your iPhone, iPad or iPod touch.
Tap [Settings] - [Privacy] - [Photos] and check whether PCS Manager is allowed to access photos.