Shuffle button is gray and can't click on it

Greetings,

For my matching drag-and-drop questions I set up this matching challenge and have choices a,b,c,d mapped out to their correct answers.

I cant show the learner all the correct answers already matched up with their choice terms.

I need to randomize the answer sections so I'm not giving the learner the correct answer.

I think you achieve this by using the Shuffle button? 

Mine is gray no matter where i click my mouse i can never activate shuffle.

Not sure what I did wrong here :-(