Multi window on my Galaxy S 4 Active doesn't work ...

[jpinto]

When I press the Multi window icon on the notifications bar it stays grey, doesn't turn green. It's a brand new phone (At&t) and I upgraded the OS to kit kat. Can someone help me figuring this issue out?
Thank you

 

[Dubg]

Have you tried to press and hold the back button on the lower right hand corner of the phone? That is another way to toggle that off and on.

 

[prolongExistence]

You can also long press the toggle button in the notification bar to bring up the Display menu. In there, there is a Multi window check box. Make sure it is checked. If you don't like the shortcut, you can also get here by going Settings>My device tab>Display