DispatcherTimer not firing in WPF Application

I am trying to understand why the DispatcherTimer contained within SingletonWithTimer is not firing in the following WPF application. I've been researching this for a couple of days and cannot seem to get to the bottom it. This application is the reduced essential parts of an existing application that I'm trying to fix. The Startup object of this project is WPFApplication5TimerTest.Program.

The output in the console lists as follows, the problem is evident because the word "TimerTick" is not shown in the output:

Timer is initialized
'WpfApplication5TimerTest.vshost.exe' (Managed (v4.0.30319)): Loaded 'C:\Windows\Microsoft.Net\assembly\GAC_MSIL\PresentationFramework.Aero\v4.0_4.0.0.0__31bf3856ad364e35\PresentationFramework.Aero.dll', Skipped loading symbols. Module is optimized and the debugger option 'Just My Code' is enabled.
Sample thread
Sample thread
Sample thread
Sample thread
Sample thread
Sample thread
The thread '<No Name>' (0x10b0) has exited with code 0 (0x0).
Sample thread exiting!

This is Program.cs:

using System;

namespace WpfApplication5TimerTest
{
    static class Program
    {
        [STAThread]
        static void Main(string[] args)
        {
            AppObject = new App();
            AppObject.Run();
        }

        public static App AppObject
        {
            get;
            private set;
        }
    }
}

This is App.xaml.cs:

using System;
using System.Threading;
using System.Windows;

namespace WpfApplication5TimerTest
{
    public partial class App : Application
    {
        protected override void OnStartup(StartupEventArgs e)
        {
            var sampleThread = new Thread(new ThreadStart(SampleThreadEntryPoint));            
            sampleThread.Start();
            new MainWindow().Show();
        }

        private void SampleThreadEntryPoint()
        {
            SingletonWith