Firebase Ml kit face recognition is not working with FirebaseVisionFaceDetectorOptions object but working fine in default mode

When I am using the FirebaseVisionFaceDetector object without any FirebaseVisionFaceDetectorOptions, it is able to detect faces but when I am using FirebaseVisionFaceDetectorOptions object, it is not able to detect objects please tell me if anything is missing.

I have already tried changing many options such as all classifications enable tracking all contours but still not working

 val opt = FirebaseVisionFaceDetectorOptions.Builder()
                            .setPerformanceMode(FirebaseVisionFaceDetectorOptions.FAST)
                            .setContourMode(FirebaseVisionFaceDetectorOptions.ALL_CONTOURS)
                            .enableTracking()
                            .build()

    val detector = FirebaseVision.getInstance()
                            .getVisionFaceDetector(opt)

when I am passing opt object, it is not able to detect any faces.