Why do none of my buttons work?

Unity Engine
1

I am making a 2D game, but none of the buttons seem to work. Here is my button in the inspector on Unity 2019.3:

5939999--635780--upload_2020-6-4_16-34-8.png
5939999--635780--upload_2020-6-4_16-34-8.png371×814 38.2 KB
5939999--635783--upload_2020-6-4_16-34-42.png
And here is the code for PageOne.cs:

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

public class PageOne:MonoBehaviour {
    public Rigidbody2D body;
    // Start is called before the first frame update
    void Start(){ body = GetComponent<Rigidbody2D>(); }
    public void Roll(){ body.gravityScale = 1; }
    // Update is called once per frame
    void Update(){}
}
2

check if you have an object on your scene called event system