Can't Get Character to Jump Utilizing Tags

Hi,
I’m trying to get my character to jump using the space bar for a 2D platformer but it won’t work. Any ideas?

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

public class JumpnMove : MonoBehaviour
{
    public float speed;
    private Rigidbody2D rigidbody;

    public float jumpForce;
    bool isJumping;

    void Start()
    {
        rigidbody = GetComponent<Rigidbody2D>();
    }

    void fixedUpdate()
    {
        float move = Input.GetAxis("Horizontal");
        rigidbody.velocity = new Vector2(speed * move, rigidbody.velocity.y);
        Jump();
    }
    void Jump()
    {
        if (Input.GetKeyDown(KeyCode.Space) && !isJumping)
        {
            isJumping = true;
            rigidbody.AddForce(new Vector2(rigidbody.velocity.x, jumpForce));
          
        }
    }
    void OnCollisionEnter2D(Collision2D other)
    {
        if (other.gameObject.CompareTag("Platform"))
        {
            isJumping = false;
            rigidbody.velocity = Vector2.zero;
        }
    }
}

My base is set as Platform tag. I have no idea why it won’t jump.

Try adding another parameter in your rigidbody.AddForce argument like ForceMode.Impulse or ForceMode.Force. Here is what i do for my jump: rb.AddForce(new Vector2(0, jumpForce), ForceMode2D.Force);

Also, make sure isJumping actually is switching from true to false when it is supposed to.