why is collider not colliding?

i am making an enemy AI but for some reason the enemy pass through any wall even if they have colliders on them but he does not pass through the floor. I am guessing that i dont use the proper way to do this so i want to know what i have done wrong and how should i do this.

here is the part of the code that control the movement :

function Update () { var playerDist = Vector3.Distance(player.position, transform.position);

     if (playerDist <= chaseDist )
    {
      state = "chase"; 
    } else 
    {
      state = "patrol";
    }
   

    if(state == "patrol")
    {
      Debug.Log("patrol");
      transform.Rotate(0, wanderRotation, 0);
         vectorSpeed = 1;
         transform.Translate(Vector3.forward * Time.deltaTime);
         
         crt += Time.deltaTime;
         if (crt >= 3)
         {
         wanderRotation =0;
         }
         if (crt >= 15)
         {
         wanderRotation = Random.Range(2,-2);
         crt = 0;
         }
    } 
    if (state == "chase")
    {
      Debug.Log("chasing");
      Local(player);
      vectorSpeed = 2;
    }
     

}

function FixedUpdate(){
moveDirection = Vector3(0, 0, vectorSpeed); moveDirection = transform.TransformDirection(moveDirection); moveDirection = speed; moveDirection.y -= gravity Time.deltaTime;

         var controller : CharacterController = GetComponent(CharacterController);

var flags = controller.Move(moveDirection Time.deltaTime); grounded = (flags & CollisionFlags.CollidedBelow) != 0; if (controller.collisionFlags & CollisionFlags.Sides) { vectorSpeed = 0; if (grounded) { moveDirection.y += jumpSpeed Time.deltaTime; } } }