Since upgrading to iOS 9.1 my iPad mini does not work
One of the things that they always tell you to try is to do either do a full backup to iTunes or iCloud and doing a full iPad reset &amp; restore. (Settings -> General -> Reset -> Reset All etc)

But obviously be careful about what apps you have and whether there is data that won't get backed up. There is no 'revert'.

Eliminating the possibility of a software problem is easier for you than determining a hardware problem. If you still have the problem after a full restore...

Do you have warranty?