@haxe75 It would be easier to help if you show more of your animation code than just that if it exists. If that is all your animation code then that would mean you are not actually starting your animations with something like animation.play("Idle");
Another problem I see is the 4th parameter in "Idle" is for looping which I imagine you want, so it should be..
animation.add("Idle", [0, 1] 2, true );
Then when you want to play the walking animation you say animation.play("WalkLeft"); or right.. while making sure you revert back to playing Idle when you are idle.