Bug my character does not jump

my code
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;

public class CharacterController : MonoBehaviour
{
Rigidbody2D rb;

public float jumpForce, speed;
public Transform groundCheck;
public LayerMask layerGround;
public float horizontalspeed;
// Start is called before the first frame update
void Start()
{
rb = GetComponent<Rigidbody2D>();
Input.multiTouchEnabled = true;
}

public void LeftButtonDown()
{
speed = -horizontalspeed;
}

public void RightButtonDown()
{
speed = horizontalspeed;
}

public void Stop()
{
speed = 0;
}

public void Jump()
{
if (Physics2D.OverlapCircle(groundCheck.position, 0.1f, layerGround))
rb.velocity = new Vector2(rb.velocity.x, jumpForce);
}

// Update is called once per frame
void FixedUpdate()
{
rb.velocity = new Vector2(speed, rb.velocity.y);
}

}
the character only moves left and right

 

https://imgur.com/a/YoTuNwr