Update Error Oledb C#

Question

I cannot use the UPDATE command more than once.

(https://drive.google.com/file/d/1xyqp6rA4Rk3AvneFaUlqk6AVvjQjbtSi/view?usp=drivesdk)

(https://drive.google.com/file/d/190WFQ0cxGWYJw2aO66xBNvOsNftY7CAk/view?usp=drivesdk)

(https://drive.google.com/file/d/1-XS3NeZm7cU0_4Pi7r2fY4dCNNAjCKtf/view?usp=drivesdk)

For example, when I do the update on id 43, sure. But when I try to finish 44, it does not finish, but 43 that gets the update..

Code:

Int att,index;

Private void Datagrid_cellclick(Object Sender, Datagridviewcelleventsargs and) {

   if(e.RowIndex >= 0)
   {

         Index = e.RowIndex;                                               
         att = Convert.ToInt32(DataGrid.Rows[Index].Cells[0].Value);

}
} //when I click on a cell, Att receives the number that is//within it, in the case of the ID in the database tb. And index receives the index of the line.

private void Btnfnz_Click(objetc sender, EventArgs e)
{
     If(index >=0)
     {
          var linha = DataGrid1.Rows[index];
          cn.Connection = Conexão.conectar();
          cn.CommandText = "UPDATE Atendimento SET HorarioOut = ' " + Txthr.Text + " ' WHERE ID=@att";
          cn.Parameters.AddWithValue("@att",att);
          cn.ExecuteNonQuery();
          cn.Connection = Conexão.desconectar();
     }
     else 
     {
           MessageBox.Show("Lista vazia!");
     }
     Refreshatt(); //Carrega o datagrid com dados do banco dados, onde horarioOut estiver em branco.
}

Everything works fine, but when I try to do a new update, it does, but in msm ID, it is fixed in the first ID I did the update.