Label visibility get false in blinking state in winform.

public partial class Form1 : Form
    { 
 protected System.Windows.Forms.Timer _timer;
       static int flaggg;

        private void Form1_Load(object sender, EventArgs e)
        {
           _timer = new System.Windows.Forms.Timer();
           this._timer.Interval = 700;
           this._timer.Start(); 
           this._timer.Tick += new EventHandler(_timer_Tick);
        }


public void _timer_Tick(object sender, EventArgs e)
        {
            this.lblmflash.Visible = !this.lblmflash.Visible;
           // this.lblmflash.Visible = true;
            lblmflash.ForeColor = Color.DarkGreen;
           
            if (flaggg == 1)
            {
                Appendlblmflash("Process completed, Send Another Indent");
                flaggg = 0;
            }
            //this.lblmflash.Visible = false;
        }

  public void GetData() // to run server //
        {
          string res = System.Text.Encoding.ASCII.GetString(temp);

          switch (res.Substring(0, 1))
          {
            case "O":
            if (res.StartsWith("OUTPROCESS"))
            {
                flaggg = 1;
            }
            break;
          }
        }

private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {
            Appendlblmflash("Indent in process! Please wait...");
            
        }

 public void Appendlblmflash(string val)
        {
            if (InvokeRequired)
            {
              this.Invoke(new Action<string>(Appendlblmflash), new object[] { val });
              return;
            }
            lblmflash.Text = val;
        }
}