This occurs if you have enabled "iCloud Photo Library" on your device.
How To Fix
1. Go into 'Photos' app.
2. Go to the image you want to use.
3. Tap "Edit" - To edit the image.
4. A 'downloading' alert should briefly appear.
5. Head back to Social Dummy.
6. Import again and the image should now load as expected.
This is unfortunately beyond my control. Due to privacy and no function to do this 'behind the scenes' which is why you have to explicitly do this yourself.
In v4.4.4 and later, you will be alerted of this.
Customer support service by UserEcho