Amazon ec2 无法运行任务验证字符串为空

我正在尝试使用以下JSON配置在Amazon EC2上为postgres sql创建一个简单的任务：

{
  "requiresAttributes": [],
  "taskDefinitionArn": "arn:aws:ecs:us-east-1:870465292454:task-definition/Application:2",
  "networkMode": "bridge",
  "status": "ACTIVE",
  "revision": 2,
  "taskRoleArn": null,
  "containerDefinitions": [
    {
      "volumesFrom": [],
      "memory": 512,
      "extraHosts": null,
      "dnsServers": null,
      "disableNetworking": null,
      "dnsSearchDomains": null,
      "portMappings": [
        {
          "hostPort": 5432,
          "containerPort": 5432,
          "protocol": "tcp"
        }
      ],
      "hostname": null,
      "essential": true,
      "entryPoint": null,
      "mountPoints": [],
      "name": "postgres",
      "ulimits": null,
      "dockerSecurityOptions": null,
      "environment": [
        {
          "name": "POSTGRES_PASSWORD",
          "value": "*******"
        }
      ],
      "links": [],
      "workingDirectory": null,
      "readonlyRootFilesystem": null,
      "image": "postgres",
      "command": null,
      "user": null,
      "dockerLabels": null,
      "logConfiguration": null,
      "cpu": 0,
      "privileged": null,
      "memoryReservation": null
    }
  ],
  "placementConstraints": [],
  "volumes": [
    {
      "host": {
        "sourcePath": "/var/lib/postgresql/data"
      },
      "name": "PGDATA"
    }
  ],
  "family": "Application"
}

但是，当我尝试运行此任务时，服务器会将“

无法运行任务验证字符串为空”作为响应

有人能帮我理解我在这里遗漏了什么。
错误信息非常严重。。。但在配置集群之前，我收到了此错误消息。确保在创建任务时选择了集群