AnimNotWorking

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class Coın : MonoBehaviour
6. {
7.     Animator CoinAnimm;
8.     void Start()
9.     {
10.         CoinAnimm = GetComponent<Animator>();
11.     }
12.  
13.  
14.      void OnCollisionEnter(Collision collision)
15.     {
16.         if (collision.gameObject.tag == "Finish")
17.         {
18.             CoinAnimm.SetBool("Conanim", true);
19.         }
20.     }
21. }
22.  

why animation doesn't work with this code?
but if(GetMouseButtonDown(0))
{
CoinAnimm.SetBool("Conanim", true);
}
It works when you do it with.