Instantiate animated objects in C#

When the zombie spawns, only the first zombie starts to animate but it doesnt continue to work. After the second zombie spawns, they all dont even animate. help?

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

public class spawnZombie : MonoBehaviour
{
    public float timeCounter;
    public GameObject zombie;

    public void Start()
    {
        timeCounter = Random.Range(5, 10);
    }

    public void Update()
    {
        timeCounter -= Time.deltaTime;

        if (timeCounter <= 0)
        {
            GameObject zombieClone = Instantiate(zombie, transform.position, transform.rotation) as GameObject;
            timeCounter = Random.Range(5, 10);
        }
    }
}

Probably not this script that’s causing you problems.
What does your zombie script or the object look like, other components etc.