That's what you can try to access iTunes Store (again):
Make sure your date, time, and time zone are correct in Settings > General > Date & Time.
Make sure that your iOS software is up to date by tapping Settings > General > Software Update (iOS 5 or later) or connecting your iOS device to iTunes and clicking Check for Update on your device's Summary page.
Check and verify that you're in range of a Wi-Fi router or base station. If you're on a device with cellular service, make sure that cellular data is turned on from Settings > General > Cellular.
Make sure that you have an active Internet connection. You can check the user guide for your device for help with connecting to the Internet.
Make sure that other devices (portable computers, for example) are able to connect to the Wi-Fi network and access the Internet.
Try resetting (turning off and then on again) your Wi-Fi router.
If the issue persists, try troubleshooting your Wi-Fi networks and connections.
(Apple Support)