未经授权的Microsoft Graph Api无法获取数据

我目前正在开发一个ASP.NET MVC 5站点，该站点使用Microsoft Graph API应用程序检索数据并将数据插入Microsoft Planner . 所述站点已具有Azure Active Directory身份验证 . 我目前正在使用以下代码来获取访问令牌以登录Graph API应用程序 .

public async Task<ActionResult> SignIn()
    {
        AuthenticationContext authContext = new AuthenticationContext("https://login.microsoftonline.com/common");
        string redirectUri = Url.Action("Authorize", "Planner", null, Request.Url.Scheme);
        Uri authUri = await authContext.GetAuthorizationRequestUrlAsync("https://graph.microsoft.com/", SettingsHelper.ClientId,
                                                              new Uri(redirectUri), UserIdentifier.AnyUser, null);

        // Redirect the browser to the Azure signin page
        return Redirect(authUri.ToString());
    }

    public async Task<ActionResult> Authorize()
    {
        // Get the 'code' parameter from the Azure redirect
        string authCode = Request.Params["code"];

        // The same url we specified in the auth code request
        string redirectUri = Url.Action("Authorize", "Planner", null, Request.Url.Scheme);

        // Use client ID and secret to establish app identity
        ClientCredential credential = new ClientCredential(SettingsHelper.ClientId, SettingsHelper.ClientSecret);

        TokenCache fileTokenCache = new FilesBasedAdalV3TokenCache("C:\\temp\\justin.bin");
        AuthenticationContext authContext = new AuthenticationContext(SettingsHelper.AzureADAuthorityTenantID, fileTokenCache);
        AuthenticationResult authResult = null;
        try
        {
            // Get the token silently first
            authResult = await authContext.AcquireTokenAsync(SettingsHelper.O365UnifiedResource, credential);
        }
        catch (AdalException ex)
        {
            authContext = new AuthenticationContext(SettingsHelper.AzureADAuthority, fileTokenCache);

            authResult = await authContext.AcquireTokenByAuthorizationCodeAsync(
            authCode, new Uri(redirectUri), credential, SettingsHelper.O365UnifiedResource);

            return Content(string.Format("ERROR retrieving token: {0}", ex.Message));
        }
        finally
        {
            // Save the token in the session
            Session["access_token"] = authResult.AccessToken;
        }

        return Redirect(Url.Action("Index", "Planner", null, Request.Url.Scheme));
    }

上面的代码获得访问令牌没有任何问题 . 我可以毫无问题地获取活动目录的所有用户，并将它们存储在数据库中 . 但是，当我尝试获取与任务相关的任何数据时，我会继续收到以下错误

{  
   StatusCode:401,
   ReasonPhrase:'Unauthorized',
   Version:1.1,
   Content:System.Net.Http.StreamContent,
   Headers:{  
      Transfer-Encoding:      chunked request-id:40      b53d20-c4fc-4614-837b-57a6bebb8d79 client-request-id:40      b53d20-c4fc-4614-837b-57a6bebb8d79 x-ms-ags-diagnostic:{  
         "ServerInfo":{  
            "DataCenter":"North Europe",
            "Slice":"SliceC",
            "Ring":"2",
            "ScaleUnit":"000",
            "Host":"AGSFE_IN_17",
            "ADSiteName":"NEU"
         }
      }      Duration:28.4537      Strict-Transport-Security:      max-age=31536000 Cache-Control:      private Date:Fri,
      07      Dec 2018 14:12:50      GMT Content-Type:application/json
   }
}

我检查了azure应用程序，它具有完全访问权限 . 任何有关这方面的帮助将不胜感激