ADAL令牌获取异常

我已经按照下面的示例实现了Azure AD认证:

https://github.com/Azure-Samples/active-directory-dotnet-webapp-webapi-openidconnect

这是我的应用程序的代码。用户获得间歇异常"静默获取令牌失败"。调用方法令牌获取"。如有任何帮助，我将不胜感激。

app.UseOpenIdConnectAuthentication(new OpenIdConnectAuthenticationOptions
        {
            ClientId = ClientId,
            Authority = Authority,
            Notifications = new OpenIdConnectAuthenticationNotifications()
            {
                AuthorizationCodeReceived = (context) =>
                {
                    string userObjectId = null;
                    var code = context.Code;
                    var currentClaimsIdentity = context.AuthenticationTicket.Identity;
                    if (currentClaimsIdentity != null)
                    {
                        userObjectId = currentClaimsIdentity.FindFirst(Constants.ObjectIdentifierClaimType).Value;
                    }
                    ClientCredential credential = new ClientCredential(ClientId, AppKey);
                    AuthenticationContext authContext = new AuthenticationContext(Authority, new SessionCache(userObjectId, HttpContext.Current));
                    authContext.AcquireTokenByAuthorizationCode(code, StandardSettings.ReplyUrl, credential, Constants.GraphResourceBaseUrl);
                    return Task.FromResult(0);
                },
                AuthenticationFailed = context =>
                {
                    context.HandleResponse();
                    context.Response.Redirect("/");
                    return Task.FromResult(0);
                }
            }
        });

/// <summary>
    /// Gets the access token.
    /// </summary>
    /// <returns>The access token for service call.</returns>
    private string GetAccessToken()
    {
        string userName = null;
        AuthenticationResult authenticationResult = null;
        ClaimsPrincipal currentClaimsPrincipal = ClaimsPrincipal.Current;
        if (currentClaimsPrincipal != null)
        {
            userName = currentClaimsPrincipal.FindFirst(ClaimTypes.Name).Value;
        }
        try
        {
            authenticationResult = this.GetAuthenticationResult();
            if (authenticationResult.ExpiresOn < DateTimeOffset.UtcNow)
            {
                Trace.TraceWarning("Access token expired for the user: {0}. Challenge the user authentication to get a new token.", userName);
                this.httpCurrentContext.GetOwinContext().Authentication.Challenge(OpenIdConnectAuthenticationDefaults.AuthenticationType);
            }
        }
        catch (AdalSilentTokenAcquisitionException ex)
        {
            Trace.TraceWarning("Failed to acquire the token for the user: {0} with exception: {1}. Challenge the user authentication for retry.", userName, ex);
            this.httpCurrentContext.GetOwinContext().Authentication.Challenge(OpenIdConnectAuthenticationDefaults.AuthenticationType);
        }
        if (authenticationResult == null)
        {
            try
            {
                authenticationResult = this.GetAuthenticationResult();
            }
            catch (Exception ex)
            {
                Trace.TraceWarning("Failed to acquire the token on the retry for the user: {0} with the exception: {1}.", userName, ex);
                throw new AdalException(
                    AdalError.FailedToAcquireTokenSilently,
                    "The session expired or the token cache was reset. Please sign out and then navigate to the url again to re-authenticate.");
            }
        }
        return authenticationResult.AccessToken;
    }
    /// <summary>
    /// Get the authentication result for the request.
    /// </summary>
    /// <returns>The authentication result.</returns>
    private AuthenticationResult GetAuthenticationResult()
    {
        string userObjectId = null;
        ClaimsPrincipal currentClaimsPrincipal = ClaimsPrincipal.Current;
        if (currentClaimsPrincipal != null)
        {
            userObjectId = currentClaimsPrincipal.FindFirst(Constants.ObjectIdentifierClaimType).Value;
        }
        AuthenticationContext authContext = new AuthenticationContext(
                   Startup.Authority,
                   new SessionCache(userObjectId, this.httpCurrentContext));
        ClientCredential credential = new ClientCredential(Startup.ClientId, Startup.AppKey);
        return authContext.AcquireTokenSilent(
            Constants.GraphResourceBaseUrl,
            credential,
            new UserIdentifier(userObjectId, UserIdentifierType.UniqueId));
    }