Retrieve Envelope Information with ETTN Number for the Invoice

var options = new RestClientOptions("https://apitest.nilvera.com")
{
  MaxTimeout = -1,
};
var client = new RestClient(options);
var request = new RestRequest("/einvoice/Purchase/17ae561f-2b79-4c7d-b74e-0aa861b1ad33/EnvelopeInfo", Method.Get);
request.AddHeader("Authorization", "Bearer <API KEY>");
RestResponse response = await client.ExecuteAsync(request);
Console.WriteLine(response.Content);