I just upgraded my original iPad to iOS 9.1 and it now cannot connect to the App Store. No other error is given. If I go to the App Store I get a blank page. If I try to Update an app, the screen spins for a long time and eventually gives a pop up message reading "Unable to Connect to the App Store". The connectivity of the iPad is fine and I can use other networked applications such as Safari with no problem. It is only the App Store that is not working.
How can I diagnose the cause of this problem?
Update: I signed out of the App Store by going to Settings / iTunes & App Sotre / Signout. Now, when I try to sign in, the machine hangs for about two minutes and then presents a message box that says: "Cannot connect to the iTunes Store".