My player wont jump (2d game)

I tried everything, but the player wont jump. Can you help?

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.Events;
 
 public class PlayerControler : MonoBehaviour
 {
     private Rigidbody2D PlayerRigidbody2D;
 
     public float speed = 10f;
     public float JumpForce;
     private float MoveInput;
 
     private bool FacingRight = true;
     private SpriteRenderer mySpriteRenderer;
 
     private bool IsGrounded;
     public Transform groundCheck;
     public float checkRadius;
     public LayerMask whatIsGround;
 
     private int extraJump;
     public int MaxJumps;
 
     void Start()
     {
         extraJump = MaxJumps;
         mySpriteRenderer = GetComponent<SpriteRenderer>();
         PlayerRigidbody2D = GetComponent<Rigidbody2D>();
     }
 
     void FixedUpdate()
     {
         MoveInput = Input.GetAxisRaw("Horizontal");
         PlayerRigidbody2D.velocity = new Vector2(MoveInput * speed, transform.position.y);
         if(MoveInput > 0 && FacingRight == false)
         {
             mySpriteRenderer.flipX = false;
             FacingRight = true;
         } else if(MoveInput < 0 && FacingRight == true)
         {
             mySpriteRenderer.flipX = true;
             FacingRight = false;
         }
     }
     void Update()
     {
         IsGrounded = Physics2D.OverlapCircle(groundCheck.position, checkRadius, whatIsGround);
         if (IsGrounded == true)
         {
             extraJump = MaxJumps;
         }
         if(Input.GetKeyDown(KeyCode.UpArrow) && extraJump > 0)
         {
             PlayerRigidbody2D.velocity = Vector2.up * JumpForce;
             extraJump--;
         } else if(Input.GetKeyDown(KeyCode.UpArrow) && extraJump == 0 && IsGrounded == true)
         {
             PlayerRigidbody2D.velocity = Vector2.up * JumpForce;
         }
     }
 
 }