リフレクションでプライベートメソッドを呼び出したい

maintenanceのch1 を3に変更できたのですが、その後、プライベートメソッドを呼び出せません。DeviceStatusNotify等元のクラスは変更できません。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Maintenance
{
    public partial class BaseForm : Form
    {
         public BaseForm()
        {
            InitializeComponent();
        }
    }
}
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Maintenance {
    public partial class Maintenance : Form {
        public Maintenance(BaseForm baseForm) {
            InitializeComponent();
            baseFormInstance = baseForm;
            ch1 = 2;
        }
        private int ch1;
        private int CH1;
        private static BaseForm baseFormInstance;

        private void DeviceStatusNotify() {
            CH1 = ch1;
        }
    }
}
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Maintenance;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Reflection;
using System.Windows.Forms;

namespace Maintenance.Tests
{
    [TestClass()]
    public class MaintenanceTests
    {
        public static BaseForm expected_BaseFormInstance;
        [TestMethod()]
        public void BaseFormInstanceTest()
        {
            BaseForm baseForm = new BaseForm();
            Maintenance maintenance = new Maintenance(baseForm);

            //maintenanceのch1 には2がはいっているのを確認

            var t = maintenance.GetType();
            var f = t.GetField("ch1", BindingFlags.NonPublic | BindingFlags.Instance);
            int f1 = (int)f.GetValue(maintenance);

            //maintenanceのch1 を3に変更する

            f.SetValue(maintenance, 3);  
            f1 = (int)f.GetValue(maintenance);

            //maintenanceのメンバ変数を変更してDeviceStatusNotifyを呼びたい。 DeviceStatusNotify等元のクラスは変更できない
            t = maintenance.GetType();
            //下記、うまく動かない
            t.InvokeMember("DeviceStatusNotify", BindingFlags.InvokeMethod, null, null, new object[] { maintenance });

        }
    }
}