why i can't enable private mode

[AC Question]

Hey i am using galaxy alpha (4.4.4 kitkat) and i can't enable private mode....every time i try to enable private mode a message pop up on the screen "failed to enable private mode" anyone has sollution?

 

[B. Diddy]

Welcome to Android Central! Does this happen in Safe Mode as well? Support - AT&T Cell Phones SM-G850A | Samsung Cell Phones