Why the StartCoroutine(GameOver()); don't work

Questions & Answers
1

Why the StartCoroutine(GameOver()); don’t work
my code
using System.Collections;
using System.Collections.Generic;
using UnityEngine.SceneManagement;
using UnityEngine.UI;
using UnityEngine;

public class P_Collide : MonoBehaviour {

public int Moneys;
public GameObject MoneyUI;
public static int health = 3;
public AudioClip CollectMoney;
public AudioClip pain;

// Update is called once per frame
void Update () {
    if (health <= 0)
    {
        StartCoroutine(GameOver());
    }
}
private void OnTriggerEnter2D(Collider2D trig)
{
    if (trig.gameObject.tag == "Money")
    {
        GetComponent<AudioSource>().PlayOneShot(CollectMoney, 0.5f);
        Moneys++;
        MoneyUI.GetComponent<Text>().text = (Moneys.ToString());
        Destroy(trig.gameObject);
    }
    if (trig.gameObject.tag == "log")
    {
        TakeDamage();
    }
}

void TakeDamage()
{
    GetComponent<AudioSource>().PlayOneShot(pain, 0.5f);
    health--;
}

IEnumerable GameOver ()
{
    yield return new WaitForSeconds(1.0f);
    SceneManager.LoadScene("Main");
    yield return null;
}

}

2

Also note:

IEnumerator GameOver() { // code here }

3

public GameObject Player;
public GameObject Money;

public GameObject BigTree;
public GameObject[] Rocks;
public GameObject[] debrees;

private float MoneyTimer = 2.0f;
private float RockTimer = 2.0f;
private float BigTreeTimer 5.0f;

// Update is called once per frame
void Update () {
    MoneyTimer -= Time.deltaTime;
    RockTimer -= Time.deltaTime;
    BigTreeTimer -= Time.deltaTime;

    if (MoneyTimer < 0)
    {
        SpawnMoney();
    }
    if (RockTimer < 0)
    {
        SpawnRock();
    }
    if (BigTreeTimer < 0)
    {
        StartCoroutine(SpawnBigTree());
    }
}

void SpawnMoney ()
{
    GameObject Mon = Instantiate(Money, new Vector2 (Random.Range(-6.47f, 6.62f), 6),Quaternion.identity)as GameObject;
    MoneyTimer = Random.Range(0.5f, 2.5f);
}

void SpawnRock ()
{
    GameObject Roc = Instantiate(Rocks[(Random.Range(0, Rocks.Length))], new Vector2(Random.Range( -7f, 7f), 10), Quaternion.identity) as GameObject;
    RockTimer = Random.Range(0.5f, 2.5f);
    Roc.GetComponent<Rigidbody2D>().gravityScale = Random.Range(1, 3);
}
IEnumerable SpawnBigTree()
{
    BigTreeTimer = 1000;
    Vector2 spawnSpot;
    int debreeTimer = (Random.Range(20, 30));
    int spawnOnPlayerPer = (Random.Range(0, 100));
    if (spawnOnPlayerPer < 50)
    {
        spawnSpot = new Vector2(Random.Range(-7f, 7f), 20);
    }
    else
    {
        spawnSpot = new Vector2(Player.transform.position.x, 20);
    }
    while (debreeTimer > 0)
    {
        debreeTimer--;
        float t = Random.Range(0.005f, 0.1f);
        yield return new WaitForSeconds(t);
        Debug.Log("Spawned");
        GameObject debree = Instantiate(debrees[(Random.Range(0, debrees.Length))], new Vector2(spawnSpot.x + Random.Range(-1.0f, 1.0f), spawnSpot.y - 10), Quaternion.identity) as GameObject;
        yield return new WaitForSeconds(1);
        Instantiate(BigTree, spawnSpot, Quaternion.identity);
        BigTreeTimer = Random.Range(15.0f, 45.0f);
    }
    Debug.Log("Complete");
    yield return new WaitForSeconds(1);
    Instantiate(BigTree, spawnSpot, Quaternion.identity);
    BigTreeTimer = Random.Range(15.0f, 45.0f);
}

}