If you cannot see the photo preview check to make sure the app has permission to use the camera. Follow the instructions below.


Using the Settings app on your device (for apps you've already downloaded)

  1. On your device, open your main Settings app.
  2. Select Apps or Application Manager (depending on your device, this may be different).
  3. Select an app.
  4. Scroll down to "Permissions."
  5. Make sure that "Camera" is enabled
If that doesn't resolve the problem, contact support and provide your phone model and operating system version.

Source: Google Support: Review app permissions thru Android 5.9