Try resetting the App Store:
Close the App Store completely from the app switcher window by double clicking the Home button and swiping up the App Store preview pane until it disappears from the screen. You may have to look for the App Store pane by scrawling to the left.
Then sign out of the iTunes Store (in Settings).
Then do a forced restart. Hold down the Home and Wake/Sleep buttons at the same time for about 15-20 seconds until the Apple logo appears.
Then sign back into the iTunes Store.
Also you may try upgrading to 9.3.1.
It that does not work you may have to do a system restore.
First backup your device using iTunes. Then import your photos to your computer and copy all important data. Try restoring from backup first and testing it. If it does not help, you may have to restore as New and reconfigure from scratch as the backup could be corrupted. For this reason it is important to have your photos and data saved separately from the backup.
https://support.apple.com/en-us/HT201252