IdentityServer 4 Обновить токен

Question

Следующий код выдает ошибку:

An unhandled exception occurred while processing the request.
ArgumentException: Parameter is required
Parameter name: refresh_token

Я хотел бы проверить, не истек ли срок действия моего токена в определенный промежуток времени, и если это так, он обновляется автоматически. Код следует: -

 public async Task<HttpClient> GetClient()
        {
            string token = string.Empty;
            var currentContext = _contextAccessor.HttpContext;
            var _client = _factory.CreateClient();
            var expiresAt = await currentContext.GetTokenAsync("expires_at");
            if (string.IsNullOrWhiteSpace(expiresAt) || ((DateTime.Parse(expiresAt).AddSeconds(-60)).ToUniversalTime() < DateTime.UtcNow))
            {
                token = await RenewToken();
            }
            else
            {
                token = await currentContext.GetTokenAsync(OpenIdConnectParameterNames.AccessToken);
            }
            if (!string.IsNullOrWhiteSpace(token))
            {
                _client.SetBearerToken(token);
            }
            _client.BaseAddress = new Uri(Contants.APIServices);
            _client.DefaultRequestHeaders.TryAddWithoutValidation("Accept", "application/json");
            _client.DefaultRequestHeaders.TryAddWithoutValidation("Content-Type", "application/json");
            _client.DefaultRequestHeaders.TryAddWithoutValidation("User-Agent", "AnalyzerStatusCheck");

            return _client;
        }

Исключение, создаваемое в этом блоке кода (var tokenResult = await tokenClient.RequestRefreshTokenAsync (new RefreshTokenRequest)

 private async Task<string> RenewToken()
        {
            var currentContext = _contextAccessor.HttpContext;
            var response = await _cache.GetAsync();
            if (response.IsError) throw new Exception(response.Error);

            var refreshToken = await currentContext.GetTokenAsync("refresh_token");
            var tokenClient = _factory.CreateClient();

            var tokenResult = await tokenClient.RequestRefreshTokenAsync(new RefreshTokenRequest
            {
                Address = response.TokenEndpoint,
                ClientId = "ktswebclient",
                ClientSecret = "secret",
                RefreshToken = refreshToken
            });

            if (!tokenResult.IsError)
            {
                var oldToken = await currentContext.GetTokenAsync("id_token");
                var newAccessToken = tokenResult.AccessToken;
                var newRefreshToken = tokenResult.RefreshToken;
                var expiresAt = DateTime.UtcNow + TimeSpan.FromSeconds(tokenResult.ExpiresIn);

                var info = await currentContext.AuthenticateAsync("Cookies");
                info.Properties.UpdateTokenValue("refresh_token", newRefreshToken);
                info.Properties.UpdateTokenValue("access_token", newAccessToken);
                info.Properties.UpdateTokenValue("expires_at", expiresAt.ToString("o", CultureInfo.InvariantCulture));

                await currentContext.SignInAsync("Cookies", info.Principal, info.Properties);
                return tokenResult.AccessToken;
            }
            else
            {
                throw new Exception("Problem encountered while refreshing tokens.",
                    tokenResult.Exception);
            }
        }

Код IDP: -

 public static IEnumerable<Client> GetClients()
        {
            return new List<Client>()
            {
                new Client
                {
                    ClientName="KtsWeb App",
                    ClientId="ktswebclient",
                    AllowedGrantTypes= GrantTypes.Hybrid,
                    AccessTokenType = AccessTokenType.Reference,
                    AccessTokenLifetime = 120,
                    AllowOfflineAccess = true,
                    UpdateAccessTokenClaimsOnRefresh = true,                   
                    RefreshTokenUsage = TokenUsage.ReUse,
                    RedirectUris = new List<string>()
                    {
                        "https://localhost:44355/signin-oidc" //Client URL Address

                    },
                    PostLogoutRedirectUris = new List<string>()
                    {
                        "https://localhost:44355/signout-callback-oidc"
                    },
                    AllowedScopes =
                    {
                        IdentityServerConstants.StandardScopes.OpenId,
                        IdentityServerConstants.StandardScopes.Profile,
                        IdentityServerConstants.StandardScopes.Address,
                        "roles",
                        "ktswebapi",
                        "country",
                        "subscriptionlevel"
                    },
                    ClientSecrets =
                    {
                        new Secret("secret".Sha256())
                    }
                   // AlwaysIncludeUserClaimsInIdToken = true

                }
            };            
        }