Network client : cannot fire

Hi i'm new to Unity and i have a problem with my network. I'm working on player's script. This script is working for the host but I don't understand why the client's player can't fire.

To sumup my script:

 public class Player_Controller : NetworkBehaviour
 {
     [Header("AttackArea")]
     [SerializeField] GameObject attackArea;
 
  void FixedUpdate()
     {
             if (Input.GetKeyDown(KeyCode.Space))
             {
               CmdAttackSpawn();  
             }
    }
 
 
     [Command] void CmdAttackSpawn()
     {
         var gameObject = Instantiate(attackArea, transform.position, transform.rotation) as GameObject;
         NetworkServer.Spawn(gameObject);
     }
 }

As you can see he's pretty similar to the one which is in tutorial section.

I'm on Unity 5.5.0f3 and I have this problem with the NetworkManager : link text

Is this error the origin of the problem?

PS: I just noticed that when the client is connecting to the server i have an error: InvalidOperationException: out of sync