TRESTRequest JSON POST issue in Delphi - json

Question

I'm trying to send JSON POST request to an API using a TRESTClient (Delphi 10.4/Windows 10), but I'm receiving a 409 conflict indicating "No input found". Using the same code in (Delphi XE6/Windows 10) I get a REST request failed: Socket Error # 10054 Connection reset by peer.. Using WireShark I was able to see that Delphi XE6 was sending the request with TLS 1.0 and Delphi 10.4 is using TLS v1.2. The API service accepts only TLS v1.2. Is there a way to use these REST components in Delphi XE6 to deliver the request with TLS 1.2?
I beleived my problem was that I was JSON encoding all the input with the code:
// Assign JSON
sl := TStringList.Create;
sl.Add('locations=[{"address":"Test1","lat":"52.05429","lng":"4.248618"},{"address":"Test2","lat":"52.076892","lng":"4.26975"},{"address":"Test3","lat":"51.669946","lng":"5.61852"},{"address":"Sint-Oedenrode, The Netherlands","lat":"51.589548","lng":"5.432482"}]');
and then assigning it to the Request Body with RESTRequest.AddBody(sl);, whereas the API only expects the value of the locations parameter to be JSON.
I have updated the code to assign the JSON to a String and used the RESTRequest.Params.Items[0].name := 'locations'; and RESTRequest.Params.Items[0].Value := s; to add the string to the request body.
Here's my updated code:
procedure TMainForm.btn_RouteXL_PostClick(Sender: TObject);
var
s, sResult, AError: String;
jsObj: TJSONObject;
AJSONValue, jsResponse: TJSONValue;
AParameter: TRESTRequestParameter;
AStatusCode: Integer;
begin
//ResetRESTComponentsToDefaults;
s := '[{"address":"Test1","lat":"52.05429","lng":"4.248618"},{"address":"Test2","lat":"52.076892","lng":"4.26975"},{"address":"Test3","lat":"51.669946","lng":"5.61852"},{"address":"Sint-Oedenrode, The Netherlands","lat":"51.589548","lng":"5.432482"}]';
RESTClient.BaseURL := 'https://api.routexl.com/tour';
RESTClient.ContentType := 'ctAPPLICATION_X_WWW_FORM_URLENCODED';
RESTClient.Authenticator := HTTPBasic_RouteXL;
RESTRequest.Method := TRESTRequestMethod.rmPOST;
RESTRequest.Params.AddItem; //Adds a new Parameter Item
RESTRequest.Params.Items[0].name := 'locations'; //sets the name of the parameter. In this case, since I need to use 'locations=' on the request, the parameter name is locations.
RESTRequest.Params.Items[0].Value := s; //Adds the value of the parameter, in this case, the JSON data.
RESTRequest.Params.Items[0].ContentType := ctAPPLICATION_X_WWW_FORM_URLENCODED; //sets the content type.
RESTRequest.Params.Items[0].Kind := pkGETorPOST; //sets the kind of request that will be executed.
RESTRequest.Execute;
try
memo_ResponseData.Lines.Add('************JSONText*******************');
memo_ResponseData.Lines.Add(RESTResponse.JSONValue.ToString);
//Memo1.Lines.Add('JSONValue :'+RESTResponse.JSONValue.Value);
memo_ResponseData.Lines.Add('StatusText :'+RESTRequest.Response.StatusText );
memo_ResponseData.Lines.Add('StatusCode :'+IntToStr(RESTRequest.Response.StatusCode ));
memo_ResponseData.Lines.Add('ErrorMesage:'+RESTRequest.Response.ErrorMessage);
memo_ResponseData.Lines.Add('************Content*******************');
memo_ResponseData.Lines.Add(RESTRequest.Response.Content);
memo_ResponseData.Lines.Add('************Headers*******************');
memo_ResponseData.Lines.Add(RESTRequest.Response.Headers.Text);
except
on E: Exception do
begin
memo_ResponseData.Lines.Add('************Error*******************');
memo_ResponseData.Lines.Add('Error : ' +E.Message);
memo_ResponseData.Lines.Add(E.ClassName);
memo_ResponseData.Lines.Add('************Error*******************');
memo_ResponseData.Lines.Add('Error : '+RESTResponse.Content);
end;
end;
end;
I'm able to get it to work in Postman using a key-value pair, by assigning the key as locations and the value as the contents of sl as seen in the screenshot. But I'm unable to translate that to Delphi.