Camera not following a GameObject with Tag after spawned in the scene?

I am making a racing game in which the player has to select the car and it loads the scene. The camera has FindWithTag("Player").transform;. But, when the prefab spawns as a prefab(clone) The camera, is not able to follow the cars.

 #pragma warning disable 649
 namespace UnityStandardAssets.Utility
 {
     public class SmoothFollow : MonoBehaviour
     {
         public CarUIClass CarUI;
         private int gearst = 0;
         private float thisAngle = -150;
 
         // The target we are following
         [SerializeField]
         private Transform target;
         // The distance in the x-z plane to the target
         [SerializeField]
         private float distance = 10.0f;
         // the height we want the camera to be above the target
         [SerializeField]
         private float height = 5.0f;
 
         [SerializeField]
         private float rotationDamping;
         [SerializeField]
         private float heightDamping;
         private VehicleControl carScript;
 
         // Use this for initialization
         void Start() 
         {
             target = GameObject.FindWithTag("Player").transform;
         }
 
         // Update is called once per frame
         void LateUpdate()
         {
             // Early out if we don't have a target
             if (!target)
                 return;
 
             // Calculate the current rotation angles
             var wantedRotationAngle = target.eulerAngles.y;
             var wantedHeight = target.position.y + height;
 
             var currentRotationAngle = transform.eulerAngles.y;
             var currentHeight = transform.position.y;
 
             // Damp the rotation around the y-axis
             currentRotationAngle = Mathf.LerpAngle(currentRotationAngle, wantedRotationAngle, rotationDamping * Time.deltaTime);
 
             // Damp the height
             currentHeight = Mathf.Lerp(currentHeight, wantedHeight, heightDamping * Time.deltaTime);
 
             // Convert the angle into a rotation
             var currentRotation = Quaternion.Euler(0, currentRotationAngle, 0);
 
             // Set the position of the camera on the x-z plane to:
             // distance meters behind the target
             transform.position = target.position;
             transform.position -= currentRotation * Vector3.forward * distance;
 
             // Set the height of the camera
             transform.position = new Vector3(transform.position.x ,currentHeight , transform.position.z);
 
             // Always look at the target
             transform.LookAt(target);
             
         }
         public void CarAccelForward(float amount)
     {
         carScript.accelFwd = amount;
     }
 
     public void CarAccelBack(float amount)
     {
         carScript.accelBack = amount;
     }
 
     public void CarSteer(float amount)
     {
         carScript.steerAmount = amount;
     }
 
     public void CarHandBrake(bool HBrakeing)
     {
         carScript.brake = HBrakeing;
     }
     [System.Serializable]
     public class CarUIClass
     {
 
         public Image tachometerNeedle;
         public Image barShiftGUI;
 
         public Text speedText;
         public Text GearText;
 
     }
         public void ShowCarUI()
     {
         gearst = carScript.currentGear;
         CarUI.speedText.text = ((int)carScript.speed).ToString();
 
         if (carScript.carSetting.automaticGear)
         {
             if (gearst > 0 && carScript.speed > 1)
             {
                 CarUI.GearText.color = Color.white;
                 CarUI.GearText.text = gearst.ToString();
             }
             else if (carScript.speed > 1)
             {
                 CarUI.GearText.color = Color.white;
                 CarUI.GearText.text = "R";
             }
             else
             {
                 CarUI.GearText.color = Color.white;
                 CarUI.GearText.text = "N";
             }
 
         }
         else
         {
 
             if (carScript.NeutralGear)
             {
                 CarUI.GearText.color = Color.white;
                 CarUI.GearText.text = "N";
             }
             else
             {
                 if (carScript.currentGear != 0)
                 {
                     CarUI.GearText.color = Color.white;
                     CarUI.GearText.text = gearst.ToString();
                 }
                 else
                 {
 
                     CarUI.GearText.color = Color.white;
                     CarUI.GearText.text = "R";
                 }
             }
 
         }
 
 
 
 
 
         thisAngle = (carScript.motorRPM / 20) - 175;
         thisAngle = Mathf.Clamp(thisAngle, -180, 90);
 
         CarUI.tachometerNeedle.rectTransform.rotation = Quaternion.Euler(0, 0, -thisAngle);
         CarUI.barShiftGUI.rectTransform.localScale = new Vector3(carScript.powerShift / 100.0f, 1, 1);
 
     }
 
     
     }
 }