Try this
To open App Notification Settings  in android Oreo and higher (MIUI v9 and 10) you need to pass NOTIFICATION_CHANNEL_ID in intent
Here  is the working code tested in MIUI v9 and the new version 10
SAMPLE CODE
import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.content.Context;
import android.content.Intent;
import android.graphics.Color;
import android.net.Uri;
import android.os.Build;
import android.provider.Settings;
import android.support.v4.app.NotificationCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import java.util.Objects;
public class MainActivity extends AppCompatActivity {
    String NOTIFICATION_CHANNEL_ID = "Nilesh_channel";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        NotificationManager mNotificationManager =
                (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
        long pattern[] = {0, 1000, 500, 1000};
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel notificationChannel = new NotificationChannel(NOTIFICATION_CHANNEL_ID, "Your Notifications",
                    NotificationManager.IMPORTANCE_HIGH);
            notificationChannel.setDescription("");
            notificationChannel.enableLights(true);
            notificationChannel.setLightColor(Color.RED);
            notificationChannel.setVibrationPattern(pattern);
            notificationChannel.enableVibration(true);
            Objects.requireNonNull(mNotificationManager).createNotificationChannel(notificationChannel);
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
                NotificationChannel channel = mNotificationManager.getNotificationChannel(NOTIFICATION_CHANNEL_ID);
                channel.canBypassDnd();
            }
            NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID);
            notificationBuilder.setAutoCancel(true)
                    .setColor(ContextCompat.getColor(this, R.color.colorAccent))
                    .setContentTitle(getString(R.string.app_name))
                    .setContentText("Test")
                    .setDefaults(Notification.DEFAULT_ALL)
                    .setWhen(System.currentTimeMillis())
                    .setSmallIcon(R.drawable.ic_launcher_background)
                    .setAutoCancel(true);
            mNotificationManager.notify(1000, notificationBuilder.build());
        }
    }
    public void ClickMe(View view) {
        notificationSettings(NOTIFICATION_CHANNEL_ID,this);
    }
    public void notificationSettings(String channel, Context context) {
        Intent intent = new Intent();
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            if (channel != null) {
                intent.setAction(Settings.ACTION_CHANNEL_NOTIFICATION_SETTINGS);
                intent.putExtra(Settings.EXTRA_CHANNEL_ID, channel);
            } else {
                intent.setAction(Settings.ACTION_APP_NOTIFICATION_SETTINGS);
            }
            intent.putExtra(Settings.EXTRA_APP_PACKAGE, context.getPackageName());
        } else if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.N_MR1) {
            intent.setAction(Settings.ACTION_APP_NOTIFICATION_SETTINGS);
            intent.putExtra(Settings.EXTRA_APP_PACKAGE, context.getPackageName());
        } else if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP){
            intent.setAction(Settings.ACTION_APP_NOTIFICATION_SETTINGS);
            intent.putExtra("app_package", context.getPackageName());
            intent.putExtra("app_uid", context.getApplicationInfo().uid);
        } else if (Build.VERSION.SDK_INT == Build.VERSION_CODES.KITKAT) {
            intent.setAction(Settings.ACTION_APPLICATION_DETAILS_SETTINGS);
            intent.addCategory(Intent.CATEGORY_DEFAULT);
            intent.setData(Uri.parse("package:" + context.getPackageName()));
        }
        context.startActivity(intent);
    }
}