Using microsoft face recognition services faceServiceClient is getting null (using same code snippet as in documentation and sample app)

Question

using following code snippet to find similar faces via asynch task

class DetectionTask extends AsyncTask<InputStream, String, Face[]> {
        private boolean mSucceed = true;
        int mRequestCode;
        DetectionTask(int requestCode) {
            mRequestCode = requestCode;
        }

        @Override
        protected Face[] doInBackground(InputStream... params) {

            FaceServiceClient faceServiceClient = SampleApp.getFaceServiceClient();

            try{
                publishProgress("Detecting...");

                // Start detection.
                return faceServiceClient.detect(
                        params[0],  /* Input stream of image to detect */
                        true,       /* Whether to return face ID */
                        false,       /* Whether to return face landmarks */
                        /* Which face attributes to analyze, currently we support:
                           age,gender,headPose,smile,facialHair */
                        null);
            }  catch (Exception e) {
                mSucceed = false;
                publishProgress(e.getMessage());
                addLog(e.getMessage());
                return null;
            }
        }

using this following class to generate a Face service client This is my code for Sample App

public class SampleApp extends Application {
    @Override
    public void onCreate() {
        super.onCreate();
        sFaceServiceClient = new FaceServiceRestClient(getString(R.string.subscription_key));
    }

    public static FaceServiceClient getFaceServiceClient() {
        return sFaceServiceClient;
    }

    private static FaceServiceClient sFaceServiceClient;
}

While debugging I found that sFaceServiceClient is always null when calling SampleApp.getFaceServiceClient() so I don't get any response due to null object . I tried using different keys via multiple accounts but of no help . The same issue still persists. A help will be appreciated