Ionic framework 如何在ionic中以编程方式连接VPN网络

我想用ionic创建vpn配置。我尝试了此代码，但它返回

未知错误

。原因可能是什么？我能做什么

const options = {
  vpnHost: 'tt.monkeyvpn.com',
  vpnUsername: 'tester',
  vpnPassword: 'test',
  userCertificate: 'MIINmAIBAzCCDV4GCSqGSIb3DQEHAaCCDU8Egg1LMIINRzCCB78GCSqGSIb3DQEHBqCCB7AwggesAgEAMIIHpQYJKoZIhvcNAQcBMBwGCiqGSIb3DQEMAQYwDgQIQSYYmUBCA3kCAggAgIIHeFtesvIQYBMRaFk',
  caCertificate: '',
  userCertificatePassword: 'testit',
};

window['plugins'].VPNManager.enable(
  function(result) {
    console.log('result ', result);
    alert('connected');
  },
  function(error) {
    console.log('error ', error);
    alert(error);
  },
  options
);