Transactional mail with custom template does not merge params

Hi,
For a few days now, the transactional emails sent using the SendTransacEmail API have not been replacing the custom template parameters with their assigned values. From the code’s perspective, everything appears to be fine, but the received email contains blank text in place of the parameters. What could be the issue?
Here is the code excerpt:
<<
//Invio una mail transazionale di notifica…
var apiInstance = new TransactionalEmailsApi();

            JObject Headers = new JObject();
            Headers.Add("Saluber-Transactional-Mail", Guid.NewGuid().ToString());
            long? TemplateId = Int32.Parse(mailTemplateId);
            JObject Params = new JObject();
            Params.Add("subject", Subject);
            Params.Add("testo_titolo_notifica", Subject);

            var testoNotifica = "";
            testoNotifica += $"E' stata riscontrata una criticità durante l'intervento con codice {work.WorkCode}.<br><br>";
            testoNotifica += $"CLIENTE: {contract.Customer.CustomerName}.<br><br>";
            testoNotifica += $"SEDE: {site.SiteName}, {site.Address ?? ""}, {site.City ?? ""}, {site.Province ?? ""}.<br><br>";
            testoNotifica += $"*** TESTO DELLA CRITICITA' RISCONTRATA ***<br>{work.Criticalities}<br><br>";
            if (salesReps != null || salesReps.Count > 0)
            {
                testoNotifica += $"*** AGENTI COMMERCIALI DI RIFERIMENTO ***<br><br>";
                foreach (var sr in salesReps)
                {
                    testoNotifica += $"{sr.firstname.ToUpper()} {sr.lastname.ToUpper()}<br>";
                }
                testoNotifica += $"<br><br>";
            }
            testoNotifica += "Puoi <a href=\"" + WEB_APP_URL + $"/Work/Edit/{work.WorkId}\" >CLICCARE QUI</a> per vedere i dettagli dell'intervento.";
            testoNotifica += "<br><br>Buon lavoro da SLIM.";
            Params.Add("testo_notifica", testoNotifica);

            var testoDettagli = "";
            //testoDettagli += $"Puoi <a href=\"" + WEB_APP_URL + "/Work/ExtraWorkRequestManager \" >CLICCARE QUI</a> per vedere le ultime richieste.";
            //testoDettagli += "\"<br><br>Buon lavoro da SLIM.";
            Params.Add("testo_dettagli", testoDettagli);

            Params.Add("testo_bottone", "VISUALIZZA INTERVENTO");
            Params.Add("button_link", WEB_APP_URL + "/Work/Edit/" + work.WorkId);
            Params.Add("button_link_text", "Visualizza intervento");

            Dictionary<string, object> _params = new Dictionary<string, object>();
            _params.Add("params", Params);
            SendSmtpEmailMessageVersions messageVersion = new SendSmtpEmailMessageVersions(To1, _params, null, null, null, Subject);
            List<SendSmtpEmailMessageVersions> messageVersions = new List<SendSmtpEmailMessageVersions>();
            messageVersions.Add(messageVersion);

            try
            {
                var sendSmtpEmail = new SendSmtpEmail(Email, To, null, null, null, null, Subject, null, null, Headers, TemplateId, Params, messageVersions, null);
                CreateSmtpEmail result = apiInstance.SendTransacEmail(sendSmtpEmail);
            }
            catch (Exception e)
            {
                Debug.WriteLine(e.Message);
                Console.WriteLine(e.Message);
                return new { success = false };
            }

Thanks in advance

Hi @saluber.marketing , thanks for posting on this community.

I guess it was working before, but not anymore. Do you still encounter this issue?