使用WebSiteManagementClient.WebHostingPlans.Create创建托管计划服务，并收到错误消息“对下层服务的请求失败”

Question

我正在使用WebSiteManagementClient.WebHostingPlans.Create创建托管计划。上周一切正常，但现在出现了此错误：Request to a downlevel service failed。有人也有这个问题，并且知道如何解决吗？

 var credentials = CertificationAuthenticationHelper.GetCredentials(args.SubscriptionId, args.Certification);
 WebSiteManagementClient webSiteManagement = new WebSiteManagementClient(credentials);
 WebHostingPlanCreateParameters param = new WebHostingPlanCreateParameters();
 param.Name = FormatNameHelper.AzureWebsiteName(args.Message.WebsiteName);
 var resService = webSiteManagement.WebHostingPlans.Create(ConfigurationHelper.WebSpaceName, param);