First, try force closing the App Store:
- Double-click the Home button.
- Swipe left or right until you have located the app you wish to close.
- Swipe the app up to close it.
And if that doesn't work, I would reset the device:
Press and hold the Sleep/Wake button and the Home button together for at least ten seconds, until the Apple logo appears.
Welcome to Apple Support Communities!
Have a good one,