Unity NavMeshAgent错误

Question

我试图让一个立方体跟随我的玩家，但是每当我运行代码时，我都会收到错误："SetDestination" can only be called on an active agent that has been placed on a NavMesh. UnityEngine.AI.NavMeshAgent.SetDestination(Vector3)

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

public class CubeFollowPlayer : MonoBehaviour {
    public GameObject target = null;
    private NavMeshAgent nma = null;

    private void Start()
    {
        nma = this.GetComponent<NavMeshAgent>();
    }
    public void Update () {
        nma.SetDestination(target.transform.position);
    }
}

我将如何解决该错误？