Unity C# コルーチンが開始されない

Unityについてです。
コルーチンが開始されないでエラーが出てしまいます。どうすればいいのでしょうか？
Coroutine 'HIHyouzi' couldn't be started!
UnityEngine.MonoBehaviour:StartCoroutine(String)
ITEMR:ITHIHyouzi() (at Assets/ITEMR.cs:24)
BattleManager:ITEMR1() (at Assets/BattleScene/Battle comand texture/BattleManager.cs:755)
ITEMR:OnMouseOver() (at Assets/ITEMR.cs:61)
UnityEngine.SendMouseEvents:DoSendMouseEvents(Int32)

コルーチンを開始しようとするとこのエラー文が出ます。

コード

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

public class ITEMR : MonoBehaviour
{
GameObject BattleManagger;
BattleManager script;
// Start is called before the first frame update
void Start()
{
transform.position = new Vector2(-5, 100);
BattleManagger = GameObject.Find("BattleManagger");
script = BattleManagger.GetComponent<BattleManager>();
}

// Update is called once per frame
void Update()
{

}
public void ITHIHyouzi()
{
    StartCoroutine("HIHyouzi");
}
public void ITHyouzi()
{
    StartCoroutine("Hyouzi");
}
IEnumerator Hyouzi()
{

        transform.position = new Vector2(-5,6);
    for (float f = 0; f < 14; f++)
    {


        transform.Translate(new Vector2(0, -0.5f));

        yield return new WaitForSeconds(0.02f);
    }
}
IEnumerator HiHyouzi()
{

    transform.position = new Vector2(-5, -1);
    for (float f = 0; f < 14; f++)
    {


        transform.Translate(new Vector2(0, -0.5f));

        yield return new WaitForSeconds(0.02f);
    }

}
private void OnMouseOver()
{
    if (Input.GetMouseButtonDown(0))
    {
        script.ITEMR1();
    }
}