OleDbConnection - object reference not set to an instance of an object

Question

I have a form an one button on it,

below is very really simple my code:

private void ConnectDb()
    {
        try
        {
            connect = new OleDbConnection();
            connect.ConnectionString = @"Provider=Microsoft.ACE.OLEDB.15.0;Data Source=MySong.accdb;Persist Security Info=false;";
            connect.Open();
            statusText.Text = "Database connected";
            command = connect.CreateCommand();
        }
        catch (Exception)
        {
            statusText.Text = "ERROR::Database failed";
        }
    }

    private void CloseConnectDb()
    {
        if (connect != null)
        {
            connect.Close();
            statusText.Text = "Database Closed";
        }
    }

    private void btnTambah_Click(object sender, EventArgs e)
    {
        DateTime tanggal = DateTime.Today;

        Band = txtArtis.Text;
        Title = txtJudul.Text;

        this.ConnectDb();
        command.CommandText = "INSERT INTO TableLagu (Tanggal, Artis, Title, Status) VALUES ('" + tanggal + "', '" + Band + "', '" + Title + "', 'Belum ada')";
        if (command.ExecuteNonQuery() != 0) //executenonquery returns number of row affected
        {
            statusText.Text = "ADD--Data Success inserted";
            txtArtis.Text = "";
            txtJudul.Text = "";


        }
        else statusText.Text = "ERROR::Insert failed";
        this.CloseConnectDb();
    }

When i click on my 'btnTambah' button, it always say "object reference not set to an instance of an object" and display "ERROR::Database failed" on its statusText.

any solution??

i think this code doesn't run while try to call ConnectDb method.

you can see my connection string

Provider=Microsoft.ACE.OLEDB.15.0; actually, when i creating it, i have microsoft access database 2013 installed on my machine. it works good.

now, i'm trying to run my application on my friends computer that microsoft access installed version 2007. and got an error like above.