Multiplayer / LocalPlayer cannot move with CharacterController, why?

Hello everybody,

I try to make a multiplayer game and have only one problem: the local player cannot move. I used a CharacterController and call it in the Start() function. In the Move() function I used controller.move . It doesnt'nt work. All the other things are working fine. Can anybody help me, please? Here is my Code:

public class PlayerControllerNetwork : NetworkBehaviour {

 public float walkSpeed;

 private bool isMoving;
 private Vector3 moveDirection;
 private CharacterController controller;

 public Camera cameraLeft, cameraRight;


 void Start()
 {
     if (isLocalPlayer)
     {
         GetComponentInChildren<OpenDiveSensor>().enabled = true;
         GetComponentInChildren<MouseLook>().enabled = true;
         GetComponentInChildren<OffsetCenter>().enabled = true;
         GetComponentInChildren<PlayerControllerScriptNetwork>().enabled = true;
         GetComponentInChildren<RaycastingForMovementPauseTrigger>().enabled = true;
         GetComponentInChildren<health>().enabled = true;
         GetComponentInChildren<StickOnObject>().enabled = true;
         GetComponentInChildren<InfoPanel>().enabled = true;
         GetComponentInChildren<CountPickups>().enabled = true;
         GetComponentInChildren<Timer>().enabled = true;

         cameraLeft.enabled = true;
         cameraRight.enabled = true;


         controller = GetComponentInChildren<CharacterController>();
         this.isMoving = false;
         moveDirection = Vector3.zero;
     }
     
 }


 void Update()
 {
     if (!isLocalPlayer)
         return;

     if (this.isMoving)
     {
         GenerateMovementVector();
         Move();
     }
     
 }
 
 
 void Move()
 {
     controller.Move(moveDirection * Time.deltaTime);
 }


 void GenerateMovementVector()
 {
     this.moveDirection = this.transform.forward;
     this.moveDirection.y = 0;
     this.moveDirection *= walkSpeed;
 }


 public override void OnStartLocalPlayer()
 {
     base.OnStartLocalPlayer();

     GetComponentInChildren<MeshRenderer>().material.color = Color.red;
 }

}