title: How to enable autolayout in storyboard Xcode 8
body: <p>I'm trying to enable autolayout by clicking on 'Use Auto Layout' on following option in storyboard<a href="https://i.stack.imgur.com/MiDec.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MiDec.png" alt="enter image description here"></a></p>
  
  <p>but after a while, it just appears a lock on screen indicating it is not possible, and checkbox is never selected</p>
  
  <p><a href="https://i.stack.imgur.com/sqe9d.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/sqe9d.png" alt="enter image description here"></a></p>
  
  <p>how to enable it properly?</p>