Multiplayer Player Prefab: NullReferenceException: Object reference not set to an instance of an object

Hi!

I have a problem! I want to test multiplayer a little bit so i set up a scene with network manager and the network identity on the player prefab! i dragged the player prefab in the slot in the network manager! the camera control is seperatly and not connected with the player prefab! offline everything works ok, but when i start the multiplayer test i get the following NullReferenceException:

NullReferenceException: Object reference not set to an instance of an object CameraOrbit.Start () (at Assets/Scripts/Camera Scripts/CameraOrbit.cs:29)

NullReferenceException: Object reference not set to an instance of an object CameraOrbit.HandleCamera () (at Assets/Scripts/Camera Scripts/CameraOrbit.cs:64) CameraOrbit.Update () (at Assets/Scripts/Camera Scripts/CameraOrbit.cs:45)

Player Movement is working correctly but the camera wont. ive tried several things now but i cant find the right solution. the error occurs in the camera script.

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class CameraOrbit : Orbit {
 
     public Vector3 targetOffset = new Vector3 (0, 2, 0);
     public Vector3 cameraPositionZoom = new Vector3 (-0.5f, 0, 0);
     public float cameraLenght = -10f;
     public float cameraLenghtZoom = -5f;
     public Vector2 orbitSpeed = new Vector2 (0.01f, 0.01f);
     public Vector2 orbitOffset = new Vector2 (0, -0.8f);
     public Vector2 angleOffset = new Vector2 (0, -0.25f);
 
     private float _zoomValue;
     private Vector3 _cameraPositionTemp;
     private Vector3 _cameraPosition;
 
     private Transform _playerTarget;
     private Camera _mainCamera;
 
     void Awake ()
     {
         
     }
 
     // Use this for initialization
     void Start () {
             _playerTarget = GameObject.FindGameObjectWithTag ("Player").transform;
 
             sphericalVectorData.Lenght = cameraLenght;
             sphericalVectorData.Azimuth = angleOffset.x;
             sphericalVectorData.Zenith = angleOffset.y;
 
             _mainCamera = Camera.main;
 
             _cameraPositionTemp = _mainCamera.transform.localPosition;
             _cameraPosition = _cameraPositionTemp;
 
     }
     
     // Update is called once per frame
     void Update () {
 
         HandleCamera ();
     }
 
     void HandleCamera ()
     {
         if ( Input.GetMouseButton (1) )
         {
             sphericalVectorData.Azimuth += Input.GetAxis ("Mouse X") * orbitSpeed.x;
             sphericalVectorData.Zenith += Input.GetAxis ("Mouse Y") * orbitSpeed.y;
 
             sphericalVectorData.Zenith = Mathf.Clamp (sphericalVectorData.Zenith + orbitOffset.x, orbitOffset.y, 0f);
         }
 
             float distanceToObject = _zoomValue;
             float deltaDistance = Mathf.Clamp (_zoomValue, distanceToObject, -distanceToObject);
             sphericalVectorData.Lenght += (deltaDistance - sphericalVectorData.Lenght);
 
             Vector3 lookAt = targetOffset;
 
             lookAt += _playerTarget.position;
 
             base.Update ();
 
             transform.position += lookAt;
             transform.LookAt (lookAt);
 
             if ( _zoomValue == cameraLenghtZoom )
             {
                 Quaternion targetRotation = transform.rotation;
                 targetRotation.x = 0f;
                 targetRotation.z = 0f;
                 _playerTarget.rotation = targetRotation;
             }
 
             _cameraPosition = _cameraPositionTemp;
             _zoomValue = cameraLenght;
     }
 }
 

ive tried to set the _playerTarget variable public and i saw that this variable stays empty after start. i think thats the problem. can anyone help? Thank you