How to access a SQL database from a Windows service?

I am trying to develop an windows service for Windows 10 (64bit), which intends to insert record in local MS SQL Server (v.11) periodically.

It installed and ran successfully, but no record is inserted. I tried both System.Timers.Timer and System.Threading.Timer.

I also tried to insert on service start event. But that also didn't work.

Here is my code:

public partial class Service1 : ServiceBase
{
    // System.Timers.Timer timer;
    System.Threading.Timer threadTimer;
   
    public Service1()
    {
        InitializeComponent();
    }


    //UPDATE: I checked the following method code in a console application. It works fine.
    private void InsertRecord()
    {
        try
        {
            using (SqlConnection connection = new SqlConnection("Server=.;Database=TestDb; Trusted_Connection=True;"))
            {
                using (SqlCommand command = new SqlCommand())
                {
                    command.Connection = connection;
                    command.CommandText = "Insert into .....')";
                    connection.Open();
                    command.ExecuteNonQuery();
                    connection.Close();
                }
            }
        }
        catch (Exception ex)
        {
        }
    }

    protected override void OnStart(string[] args)
    {
        InsertRecord(); //This line not executed also.

        TimeSpan tsInterval = new TimeSpan(0, 2, 0); //2 minute interval.
        threadTimer = new Timer(new TimerCallback(threadTimer_Elapsed)
            , null, tsInterval, tsInterval);


        //timer = new System.Timers.Timer();
        //timer.Interval = 10000;
        //timer.Elapsed += Timer_Elapsed;
        //timer.Enabled = true;
        //timer.Start();
    }

    private void threadTimer_Elapsed(object state)
    {
         InsertRecord();
    }

    //private void Timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
    //{
    //      InsertRecord()
    //}

    protected override void OnStop()
    {
        threadTimer.Change(Timeout.Infinite, Timeout.Infinite);
        threadTimer.Dispose();
        threadTimer = null;

        //timer.Stop();
    }
}

What did I miss here?