If you are using iOS 5.0 or older, please open your device's "Settings" -> "Location Service". Find iZip in the App list , and turn on its access your photos.
If you are using iOS 6.0 or later, you need to do the following steps:
Open your device's "Settings" -> "Privacy" -> "Photo Album". Find iZip in the App list, and turn on its access your photos.