My player wont jump (2d game)

Questions & Answers
1

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;
        }
    }

}
2

You should start by eliminating certain parts of your code. When did the problem start?