There are reports that iPad Pro is freezing after charging and does not respond to pressing buttons.
Some users suggest the iOS 9.1 is the source of the problem. In that case, software update iOS 9.2 should fix the issue. For now, Apple released a document explaining how to repair the issue. You can read it here. It says you need to force-restart the iPad Pro by holding the sleep/wake and home button together for 10 seconds.