Player wont Jump

Unity Engine
1

On an earlier scene my player could Jump but now he walks and nothing else…
this is my script

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PlayerMovement : MonoBehaviour
{
      public float moveSpeed;
      public bool isGrounded = false;
      public bool Ismoving = false;
      public GameObject player;

      public void Update()
      {
            Jump();
            Flip();
            Vector3 movement = new Vector3(Input.GetAxis("Horizontal"), 0f, 0f);
            Rigidbody2D rb = GetComponent<Rigidbody2D>();
            rb.velocity = new Vector2(movement.x * moveSpeed, rb.velocity.y);
      }

      public void Jump()
      {
            if (Input.GetButtonDown("Jump") && isGrounded == true) {
                  gameObject.GetComponent<Rigidbody2D>().AddForce(new Vector2(0f, 5f), ForceMode2D.Impulse);
            }
      } 

      public void Flip()
      {
            if (Input.GetKeyDown(KeyCode.RightArrow)) {
                  transform.eulerAngles = new Vector3(0, 0, 0);
            }else if (Input.GetKeyDown(KeyCode.LeftArrow)) {
                  transform.eulerAngles = new Vector3(0, 180, 0);
            }
      }

      private void OnTriggerEnter2D(Collider2D other)
      {
            if (other.gameObject.CompareTag("Platform")) {
            player.transform.parent = other.gameObject.transform;
            }
      }

      private void OnTriggerExit2D(Collider2D other)
      {
            if (other.gameObject.CompareTag("Platform")) {
            player.transform.parent = null;
            }
      }

}

and this is the isgrounded script

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Grounded : MonoBehaviour
{
    GameObject Player;

    void Start()
    {
        Player = gameObject.transform.parent.gameObject;
    }

    public void OnCollisionEnter2D(Collision2D collision2D)
    {
        if (collision2D.collider.tag == "Ground") {
            Player.GetComponent<PlayerMovement>().isGrounded = true;
        }
    }

    public void OnCollisionExit2D(Collision2D collision2D)
    {
        if (collision2D.collider.tag == "Ground") {
            Player.GetComponent<PlayerMovement>().isGrounded = false;
        }
    }
}

another thing is it now has an error saying object refernce not set to an instance of an object
its on this line Player = gameObject.transform.parent.gameObject;

2

That exception suggests that your grounded script is attached to a root gameobject; it doesn’t have a parent, so it throws null, so your player is never grounded (and can’t jump).