Android 8 notifications setSound not working

I tried to see the difference between your sound file and mine. I used Audacity software. Your sound file has sampling rate 22050Hz while the sound files i use are sampled at 44100Hz. So i converted your sound file sampling rate to 44100Hz and used that as notification sound. Now it works.

The problem is with the sound file. May be it's new change in Android O because it's working fine on older Android version.

This is how to resample-

if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
            Notification.Builder notificationBuilder =
                    new Notification.Builder(MyApplication.getInstance().getApplicationContext(), NOTIFICATION_CHANNEL_ID)
                            .setSmallIcon(R.mipmap.ic_launcher)
                            .setContentTitle(pTitle)
                            .setContentText(messageBody)
                            .setAutoCancel(true)
                            //.setPriority(Notification.PRIORITY_MAX) // this is deprecated in API 26 but you can still use for below 26. check below update for 26 API
                            //.setSound(defaultSoundUri)
                            .setContentIntent(pendingIntent);

            NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, "My Notifications", NotificationManager.IMPORTANCE_HIGH);
            // Configure the notification channel.
            AudioAttributes att = new AudioAttributes.Builder()
                    .setUsage(AudioAttributes.USAGE_NOTIFICATION)
                    .setContentType(AudioAttributes.CONTENT_TYPE_SPEECH)
                    .build();
            notificationChannel.setSound(defaultSoundUri,att);
            notificationChannel.setDescription(messageBody);
            notificationChannel.enableLights(true);
            notificationChannel.setLightColor(Color.RED);
            notificationChannel.setVibrationPattern(new long[]{0, 1000, 500, 1000});
            notificationChannel.enableVibration(true);
            notificationManager.createNotificationChannel(notificationChannel);
            if (imageThumbnail != null) {
                notificationBuilder.setStyle(new Notification.BigPictureStyle()
                        .bigPicture(imageThumbnail).setSummaryText(messageBody));
            }
            notificationManager.notify(0 /* ID of notification */, notificationBuilder.build());

        } else {
            NotificationCompat.Builder notificationBuilder =
                    new NotificationCompat.Builder(MyApplication.getInstance().getApplicationContext())
                            .setSmallIcon(R.mipmap.ic_launcher)
                            .setContentTitle(pTitle)
                            .setContentText(messageBody)
                            .setAutoCancel(true)
                            .setPriority(Notification.PRIORITY_MAX) // this is deprecated in API 26 but you can still use for below 26. check below update for 26 API
                            .setSound(defaultSoundUri)
                            .setContentIntent(pendingIntent);
            if (imageThumbnail != null) {
                notificationBuilder.setStyle(new NotificationCompat.BigPictureStyle()
                        .bigPicture(imageThumbnail).setSummaryText(messageBody));
            }
            notificationManager.notify(0 /* ID of notification */, notificationBuilder.build());

        }