Error: {"errCode":-1,"errMsg":"3rd upload or preview error, dev platform ext appid not auth"}

ci.Project({
    appid: 'wx54f97d7e33a0973e',
    type: 'miniProgram',
    projectPath: process.cwd() + '/dist',
    privateKeyPath: process.cwd() + '/scripts/private.wx54f97d7e33a0973e.key',
    ignores: ['node_modules/**/*'],
  })

ext.json:
{
  "extEnable": false,
  "extAppid": "wx54f97d7e33a0973e",
  "ext": {
    "companyId":  "G00001",
    "appId": "wx8f068b1d5fdeca1d"
  }
}

问题: 
1. privateKeyPath: 如果使用第三方平台的appid，这个从何处下载?
2. 使用绑定的小程序appid，上传会报上面的错误