I has this happen to me last night to. Ultimately, this worked:
1. Open the App Store
2. Goto the Features page.
3. Scroll all the way down to the bottom and press on the button with your Apple ID.
4. Press logout.
5. Reboot yor device (!! VERY IMPORTANT. This didn't work until I did this part).
6. Once rebooted, sign back in to your account.
There are many functions (the latest IOS added 200 new features) in the iPhone so it will take very long to troubleshoot one at a time. You can try reset which does not delete any settings:
Do a reset (Hold Sleep/Wake and Home buttons about 10 secs or more till Apple logo appears)
and see if that helps.