The Code only loads one scene then wont work on the next scene

Unity Engine
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1

So i used this code to load a scene after a scene but for some reason only work on the first scene then it wont work on the next

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

public class SceneContoller : MonoBehaviour
{
    public static SceneContoller instance;

    private void Awake()
    {
        if (instance == null)
        {
            instance = this;
            DontDestroyOnLoad(gameObject);
        }
        else
        {
            Destroy(gameObject);
        }
    }
    public void NextLevel()
    {
        SceneManager.LoadSceneAsync(SceneManager.GetActiveScene().buildIndex + 1);
    }
    public void LoadScene(string sceneName)
    {
        SceneManager.LoadScene(sceneName);
    }

}
2

That is a textbook example of a defective singleton.

If you ever find yourself asking “is this instance null?” then you are working with a defective singleton. Delete it and make one that plays nice with Unity3D.

Some super-simple Singleton examples to take and modify:

Simple Unity3D Singleton (no predefined data):

Unity3D Singleton with a Prefab (or a ScriptableObject) used for predefined data:

These are pure-code solutions, DO NOT put anything into any scene, just access it via .Instance

Alternately you could start one up with a [RuntimeInitializeOnLoad] attribute.

There is never a reason to drag a GameObject into a scene if it will be DontDestroyOnLoad.

If you do:

  • you may drag it into something else that isn’t DDOL. FAIL
  • you may drag something else into it that isn’t DDOL. FAIL

Just DO NOT drag anything into a scene that will be marked DontDestroyOnLoad. Just Don’t Do It!