Gmail Api返回错误503服务不可用

Question

我得到了此代码，该代码从我的帐户获取电子邮件。这适用于我们的自动化流程之一。但是使用另一个帐户无法获得服务错误

    private static GmailService GetGmailService()
    {
        string credPath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
        UserCredential credential;
        using (var stream =
            new FileStream(Path.Combine(credPath, "credentials.json"), FileMode.Open, FileAccess.Read))
        {
            var path = System.Environment.GetFolderPath(
              System.Environment.SpecialFolder.Personal);
            var credPath2 = Path.Combine(path, ".credentials/gmail-dotnet-quickstart.json");

            credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
                GoogleClientSecrets.Load(stream).Secrets,
                Scopes,
                "user",
                CancellationToken.None,
                new FileDataStore(credPath2, true)).Result;
        }

        var service = new GmailService(new BaseClientService.Initializer()
        {
            HttpClientInitializer = credential,
            ApplicationName = ApplicationName,

        });
        return service;
    }


    public static string GetRegistrationLink(string devEmail, string toEmail, string subjectSearch = "", string keywords = "")
    {
        var url = string.Empty;
        var service = GetGmailService();
        var inboxlistRequest = service.Users.Messages.List(devEmail);
        inboxlistRequest.LabelIds = "INBOX";

        var query = @"in:unread in:inbox subject:Reset your CS Professional Suite Web account password";
        //@"in:unread ";
        //if (!string.IsNullOrEmpty(subjectSearch))
        //    query += $"subject:{subjectSearch} ";
        //if (!string.IsNullOrEmpty(toEmail))
        //    query += $"to:{toEmail} ";
        //if (!string.IsNullOrEmpty(keywords))
        //    query += $@"{keywords}";

        //inboxlistRequest.Q = query;
        inboxlistRequest.IncludeSpamTrash = false;

        //get our emails
        var emailListResponse = inboxlistRequest.Execute();
        if (emailListResponse != null && emailListResponse.Messages != null)
        {
            //loop through each email and get what fields you want... 
            foreach (var email in emailListResponse.Messages)
            {
                var emailInfoRequest = service.Users.Messages.Get(devEmail, email.Id);
                var emailInfoResponse = emailInfoRequest.Execute();
                if (emailInfoResponse == null) continue;
                var from = "";
                var date = "";
                foreach (var mParts in emailInfoResponse.Payload.Headers)
                {
                    switch (mParts.Name)
                    {
                        case "Date":
                            date = mParts.Value;
                            break;
                        case "From":
                            @from = mParts.Value;
                            break;

                    }

                    if (date == "" || @from == "") continue;
                    var messageBodyParts = emailInfoResponse.Payload?.Parts?.SelectMany(a => a.Parts).ToList();
                    if (messageBodyParts == null) continue;
                    foreach (var p in messageBodyParts)
                    {
                        if (p.MimeType != "text/html") continue;
                        byte[] data = FromBase64ForUrlString(p.Body.Data);
                        var decodedString = Encoding.UTF8.GetString(data);
                        url = Regex.Match(decodedString, "href\\s*=\\s*\"(?<url>.*?)\"").Groups["url"].Value;
                    }
                }
            }

        }
        return url;
    }

已启用api，并且凭据已包含在项目中，但它返回503服务不可用错误。但是当我在控制台上运行相同的代码时，使用相同的凭据即可正常工作。json