C-patex api says: Invalid signature

Question

I am trying to create a crypto bot for the c-patex exchange on Pascalabc. I'm stuck on private requests using a key and a secret key. I get an error - {"error":{"code":2005,"message":"Signature is incorrect."}}

This is my code:

function GetOrders.TGetOrders.GetOrders: string;
begin
  var hmac := new HMACSHA256(Encoding.UTF8.GetBytes('xxx'));
  var timestapm := (System.IO.StreamReader.Create(System.Net.WebRequest.CreateHttp('https://c-patex.com//api/v2/timestamp.json').GetResponse.GetResponseStream).ReadToEnd.ToBigInteger * 1000).ToString;
  var sigstring := 'GET|/api/v2/orders|access_key=yyy&tonce=' + timestapm.ToBigInteger / 100 + '&market=compdoge';
  var compute  := hmac.ComputeHash(Encoding.UTF8.GetBytes(sigstring), 0, Encoding.UTF8.GetBytes(sigstring).Length);
  var signature := System.BitConverter.ToString(compute).Replace('-', string.Empty).ToLower();
  var reqstring := 'https://c-patex.com//api/v2/orders?access_key=6BckEAz52cOwpx1gfT0nByhLxkNF8uzzTFdzT8Oa' +
  '&market=compdoge' + 
  '&signature=' + signature +
  '&tonce=' + timestapm;
  Writeln(reqstring);
  try
    var request := System.Net.WebClient.Create;
    var data := request.DownloadData(reqstring);
  except
    on ex: System.Net.WebException do
    begin
      var Response := ex.Response;
      var stream := Response.GetResponseStream;
      var Reader := new System.IO.BinaryReader(Stream);
      var res := Reader.ReadBytes(stream.Length);
      var chararr := Encoding.UTF8.GetChars(res);
      var output := System.string.Create(chararr);
      Writeln(output);
    end;
  end;
end;
end.

Has anyone worked with the api of this exchange? Have you had a similar problem? Thanks in advance.