Score only adds 1 then stops counting!!

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Ball : MonoBehaviour
 {
 
     public GameObject point;
     
 
 
     // Start is called before the first frame update
     void Start()
     {
         point.SetActive(false);
     }
 
     // Update is called once per frame
     void Update()
     {
         
     }
 
 
     private void OnTriggerEnter2D(Collider2D collision)
     {
 
         if(collision.gameObject.tag == "CheckLeft")
         {
             point.SetActive(true);
             Instantiate (point, new Vector3(0,-2,0), Quaternion.identity);
             {
                 if(GameController.instance.isPoint == false && GameController.instance.EndMatch == false )
                 {
                     GameController.instance.number_PointsRight++;
                     GameController.instance.isPoint = true;
                 }
             }
         }
 
         if(collision.gameObject.tag == "CheckRight")
         {
             point.SetActive(true);
             Instantiate (point, new Vector3(0,-2,0), Quaternion.identity);
             {
                 if(GameController.instance.isPoint == false && GameController.instance.EndMatch == false )
                 {
                     GameController.instance.number_PointsLeft++;
                     GameController.instance.isPoint = true;
                 }
             }    
         }    
     }
 
      
 
 
    
 }

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class GameController : MonoBehaviour
 {
     public static GameController instance;
     public Text txt_PointRight, txt_PointLeft;
     public int number_PointsRight, number_PointsLeft;
     public bool isPoint, EndMatch;
 
 
     private void Awake()
     {
         if(instance == null)
         {
             instance = this;
         }
     }
 
     // Start is called before the first frame update
     void Start()
     {
 
 
     }
 
     // Update is called once per frame
     void Update()
     {
         txt_PointLeft.text = number_PointsLeft.ToString();
         txt_PointRight.text = number_PointsRight.ToString();
     }
 }

the the first script is attached to the ball and the second script is the gamecontroller.

its a volleyball game where when a ball collides with the ground the score should increase for the winning player, but in my case the score increases from 0 to 1 then stops counting. any help??