C# code works on localhost but not server error 503

I have an issue with the Adobe Acrobat Service API.

The code is nearly identical to the official .net example given and works when I run the application in localhost.  However on the server using the same client id and secret it fails with a message:

public static void RunDocxToPdfConvert(string pathToDocx, string pathToPDF)
            {
                  try
                  {
                        Adobe.PDFServicesSDK.auth.ICredentials credentials = new ServicePrincipalCredentials(
                         Environment.GetEnvironmentVariable("PDF_SERVICES_CLIENT_ID"),
                         Environment.GetEnvironmentVariable("PDF_SERVICES_CLIENT_SECRET"));

                        // Creates a PDF Services instance
                        PDFServices pdfServices = new PDFServices(credentials);

                        // 3) Upload the DOCX as an Asset
                        try
                        {
                              using (Stream inputStream = File.OpenRead(pathToDocx))
                              {
                                    //Blows up on the next line
                                    IAsset docxAsset = 
                                        PdfServices.Upload(inputStream,  
                                        PDFServicesMediaType.DOCX.GetMIMETypeValue());

                                    // 4) Create & submit the Create PDF job
                                    CreatePDFJob createPdfJob = new CreatePDFJob(docxAsset);

                                    string location = pdfServices.Submit(createPdfJob);
                                    // 5) Poll for result
                                    PDFServicesResponse<CreatePDFResult> response =
                                           pdfServices.GetJobResult<CreatePDFResult>(location, typeof(CreatePDFResult));

                                    // 6) Download the resulting PDF
                                    IAsset resultAsset = response.Result.Asset;
                                    StreamAsset streamAsset = pdfServices.GetContent(resultAsset);
                                    using (Stream outputStream = File.OpenWrite(pathToPDF))
                                    {
                                          streamAsset.Stream.CopyTo(outputStream);
                                    };
                              }
                        }
                        catch (Exception ex)
                        {
                              Log.Error(ex.ToString());
                        }
                  }
                  catch (ServiceUsageException ex)
                  {
                        Log.Error("Service usage exception encountered while executing operation" + ex.ToString(), ex);
                  }
                  catch (ServiceApiException ex)
                  {
                        Log.Error("Service API exception encountered while executing operation", ex);
                  }
                  catch (SDKException ex)
                  {
                        Log.Error("SDK exception encountered while executing operation", ex);
                  }
                  catch (IOException ex)
                  {
                        Log.Error("I/O exception encountered while executing operation", ex);
                  }
                  catch (Exception ex)
                  {
                        Log.Error("Unexpected exception encountered while executing operation", ex);
                  }
            }