Unityでhololens用のアプリケーションを作成しています。
AzureのTranslator Text API を使用したいのですがうまく動きません。
エラーとコードを載せますのでわかりましたら教えてください。
参考にしたサイトは https://blogs.msdn.microsoft.com/dataplatjp/2017/12/07/translator-text-api-sample/ です。

追記:2018年7月19日17時54分
回答をいただき証明書に関して無視して動作するように追加しました。
なのですが、UWPとしてアプリをビルドすることができません。
以下、エラーは4つです。
エラー1

Assets\Script\TrustAllCertificatePolicy.cs(3,42): error CS0246: The type or namespace name 'ICertificatePolicy' could not be found (are you missing a using directive or an assembly reference?)

エラー2

 Assets\Script\TrustAllCertificatePolicy.cs(6,50): error CS0234: The type or namespace name 'ServicePoint' does not exist in the namespace 'System.Net' (are you missing an assembly reference?)

エラー3

Assets\Script\TrustAllCertificatePolicy.cs(7,38): error CS0234: The type or namespace name 'X509Certificates' does not exist in the namespace 'System.Security.Cryptography' (are you missing an assembly reference?)

エラー4

Error building Player because scripts had compiler errors

エラー5

Build completed with a result of 'Failed'
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

エラー6

UnityEditor.BuildPlayerWindow+BuildMethodException: 4 errors
  at UnityEditor.BuildPlayerWindow+DefaultBuildMethods.BuildPlayer (BuildPlayerOptions options) [0x00207] in C:\buildslave\unity\build\Editor\Mono\BuildPlayerWindowBuildMethods.cs:172 
  at UnityEditor.BuildPlayerWindow.CallBuildMethods (Boolean askForBuildLocation, BuildOptions defaultBuildOptions) [0x00050] in C:\buildslave\unity\build\Editor\Mono\BuildPlayerWindowBuildMethods.cs:83 
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

以下の部分は解決済みです
OnInputClickedはHololensのinputイベントです。
Debug.logの結果はin!!まで出ていいます。
エラーが出るのは「response = httpWebRequest.GetResponse();」の部分です。(53行目)

using HoloToolkit.Unity.InputModule;
using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Net;
using UnityEngine;

public class Test : MonoBehaviour, IInputClickHandler
{
    string uri, ocpApimSubscriptionKey;
    // Use this for initialization
    void Start()
    {
        uri = GetUri("hello");
        ocpApimSubscriptionKey = "hogehoge";//key
    }

    // Update is called once per frame
    void Update()
    {

    }
    private string GetUri(string inputText)
    {
        //翻訳前の言語
        string fromLanguage = "en";
        // 翻訳語の言語
        string toLanguage = "ja";
        //利用するモデル  :空白 (=統計的機械翻訳) or generalnn(=ニューラルネットワーク)を指定
        string ModelType = "generalnn";
        //Translator Text API の Subscription Key(Azure Portal(https://portal.azure.com)から取得)

        //URIの定義(Getでパラメータを送信する為、URLに必要なパラメーターを付加)
        string uri = "https://api.microsofttranslator.com/v2/http.svc/Translate?" +
        "&text=" + Uri.EscapeDataString(inputText) +
        "&from=" + fromLanguage +
        "&to=" + toLanguage +
        "&category=" + ModelType;
        return uri;
    }
    private IEnumerator UseAPI()
    {
        //httpWebRequestの作成
        HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(uri);

        //Authorizationのためにhttpヘッダーにサブスクリプションキーを埋め込む
        httpWebRequest.Headers.Add("Ocp-Apim-Subscription-Key:" + ocpApimSubscriptionKey);

        WebResponse response = null;

        //Translator Text APIへのリクエストを実行して結果を取得
        response = httpWebRequest.GetResponse(); // **ここでエラーがはかれる**
        Debug.Log("wait");
        yield return response;
        Debug.Log("finish");
        using (Stream stream = response.GetResponseStream())
        {
            System.Runtime.Serialization.DataContractSerializer dcs =
            new System.Runtime.Serialization.DataContractSerializer(Type.GetType("System.String"));
            string translationText = (string)dcs.ReadObject(stream);
            Debug.Log(translationText);
        }
    }

    public void OnInputClicked(InputClickedEventData eventData)
    {
        Debug.Log("in!!");
        StartCoroutine(UseAPI());
    }
}

エラー内容:

TlsException: Invalid certificate received from server. Error code: 0xffffffff800b010a
Mono.Security.Protocol.Tls.Handshake.Client.TlsServerCertificate.validateCertificates (Mono.Security.X509.X509CertificateCollection certificates)
Mono.Security.Protocol.Tls.Handshake.Client.TlsServerCertificate.ProcessAsTls1 ()
Mono.Security.Protocol.Tls.Handshake.HandshakeMessage.Process ()
(wrapper remoting-invoke-with-check) Mono.Security.Protocol.Tls.Handshake.HandshakeMessage:Process ()
Mono.Security.Protocol.Tls.ClientRecordProtocol.ProcessHandshakeMessage (Mono.Security.Protocol.Tls.TlsStream handMsg)
Mono.Security.Protocol.Tls.RecordProtocol.InternalReceiveRecordCallback (IAsyncResult asyncResult)
Rethrow as IOException: The authentication or decryption has failed.
Mono.Security.Protocol.Tls.SslStreamBase.AsyncHandshakeCallback (IAsyncResult asyncResult)
Rethrow as WebException: Error getting response stream (Write: The authentication or decryption has failed.): SendFailure
System.Net.HttpWebRequest.EndGetResponse (IAsyncResult asyncResult)
System.Net.HttpWebRequest.GetResponse ()
Test+<UseAPI>c__Iterator0.MoveNext () (at Assets/Script/Test.cs:53)
UnityEngine.SetupCoroutine.InvokeMoveNext (IEnumerator enumerator, IntPtr returnValueAddress) (at C:/buildslave/unity/build/Runtime/Export/Coroutines.cs:17)
UnityEngine.MonoBehaviour:StartCoroutine(IEnumerator)
Test:OnInputClicked(InputClickedEventData) (at Assets/Script/Test.cs:68)
HoloToolkit.Unity.InputModule.InputManager:<OnInputClickedEventHandler>m__4(IInputClickHandler, BaseEventData) (at Assets/HoloToolkit/Input/Scripts/Utilities/Managers/InputManager.cs:402)
UnityEngine.EventSystems.ExecuteEvents:ExecuteHierarchy(GameObject, BaseEventData, EventFunction`1)
HoloToolkit.Unity.InputModule.InputManager:HandleEvent(BaseEventData, EventFunction`1) (at Assets/HoloToolkit/Input/Scripts/Utilities/Managers/InputManager.cs:296)
HoloToolkit.Unity.InputModule.InputManager:RaiseInputClicked(IInputSource, UInt32, InteractionSourcePressInfo, Int32, Object[]) (at Assets/HoloToolkit/Input/Scripts/Utilities/Managers/InputManager.cs:411)
HoloToolkit.Unity.InputModule.InteractionInputSource:GestureRecognizer_Tapped(TappedEventArgs) (at Assets/HoloToolkit/Input/Scripts/InputSources/InteractionInputSource.cs:971)
UnityEngine.XR.WSA.Input.GestureRecognizer:InvokeTapped(InteractionSource, InteractionSourcePose, Pose, Int32)