I have an iPad 3 with iOS 7.1. From April, 2014 I am having this strange problem. My iPad Apps won't update both manually and automatically. Every time I have to "Reset all settings" in the iPad and then only the apps would update. So please suggest how to solve this problem.
Did you Jailbreak your phone?
If no, try go to Settings->iTunes & AppStore and turn on automatic updates. And make sure you have update you iOS version and check if you have enough storage space to download update.