My iPad mini cannot rotate!!! but already unlock orientation

Is there a lock symbol at the top of the screen next to the battery indicator ? If there is, then depending on what you've got Settings > General > Use Side Switch To set to (rotation lock or mute notifications), then you can lock/unlock the rotation by the switch on the right hand side of the iPad above the volume switch, or via the taskbar : double-click the home button; slide from the left; and it's the icon far left; press home again to exit the taskbar. The function that isn't on the side switch is set via the taskbar instead : http://support.apple.com/kb/HT4085

maybe you accidentally turn on portrait lock. swipe up from the bottom of the screen (you may do this from any screen, but it's easier if you do this while not in an app) and make sure the top right icon isn't selected. it's a lock with an arrow around it in the shape of a circle.