Cant make controller.SimpleMove move my char

Hello

I try to use coroutine to move my character during 2 seconds every 2.5 seconds, the walk animation works but the character wont move

What I'm doing wrong ?

 @script RequireComponent(CharacterController)
  
     var speed:float = 5;
     var controller: CharacterController;
     var directionChangeInterval:float = 1;
     var maxHeadingChange:float = 30;
 
     var heading: float=0;
     var targetRotation: Vector3;
     var forward: Vector3;
  
     function Awake (){
     transform.eulerAngles = Vector3(0, Random.Range(0,360), 0); 
  
         //StartCoroutine
         WanderCycle();
     }
  
     function Update (){
            controller = GetComponent(CharacterController);
         transform.eulerAngles = Vector3.Slerp(transform.eulerAngles, targetRotation, Time.deltaTime * directionChangeInterval);
         forward = transform.TransformDirection(Vector3.forward);
     }
     
     function WanderCycle(){
         while(true) {
             yield Walk();
                 yield Work();
         }
     }
     
     function Walk(){
            controller.SimpleMove(forward * speed);
         animation.CrossFade("Walking",0.2);
         yield WaitForSeconds(2.0);
     }
     function Work(){
         animation.CrossFade("Working",0.2);
         yield WaitForSeconds(2.5);
     }