Some Excel Files not moving from Shared Path to SQL Server

We have an application where the data in Excel file (present in shared path) moves to Database. In case of any error, the files moves to error folder by writing the error in a log file.It uses a windows service for the operation.

Sometimes the file doesn't have any error still moves to error folder by writing log External table is not in the expected format. But the same file uploading again for once or multiple times, its moving to Database without any errors.

The windows service, DB and shared path are present in XP Server. Application was running fine all these years. But in the recent days, above mentioned problem is occurring for almost every file.

We have installed Microsoft 2003, 2007,2012 office components and access engines too. But still the issue still persists.

I am mentioning the Windows service code below. Pls help. Thanks in advance.

using System.IO;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Diagnostics;
using System.Linq;
using System.ServiceProcess;
using System.Text;
using System.Data.SqlClient;
using System.Data.OleDb;
using System.Data.Common;

namespace Impexp_Service
{
    public partial class Service1 : ServiceBase
    {
        System.Timers.Timer T1 = new System.Timers.Timer();
        public Service1()
        {
            InitializeComponent();
        }

        protected override void OnStart(string[] args)
          {
            ///start
            ///

            {
                SqlConnection strconnection = new SqlConnection();
                strconnection.ConnectionString = @"Data Source=XXXXXX;Initial Catalog=XXXX;User ID=XX;Password=XXXXXX;";
                strconnection.Open();
                // To get the all files placed at the shared path
                DirectoryInfo directory = new DirectoryInfo(@"D:\Impexp\Data\");
                FileInfo[] files = directory.GetFiles("*.xlsx");



                foreach (var f in files)
                {
                    string path = f.FullName;

                    // TO establish connection to the excel sheet
                    string excelConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + path + ";Extended Properties=\"Excel 12.0;HDR=Yes;IMEX=1\";";
                    //Create Connection to Excel work book
                    OleDbConnection excelConnection = new OleDbConnection(excelConnectionString);



                    excelConnection.Open();
                    //Create OleDbCommand to fetch data from Excel
                    OleDbCommand cmd = new OleDbCommand("Select * from [Report$]", excelConnection);

                    DbDataReader dr = cmd.ExecuteReader();
                    // OleDbDataReader dReader;
                    // dReader = cmd.ExecuteReader();
                    SqlBulkCopy sqlBulk = new SqlBulkCopy(strconnection);
                    //Give your Destination table name
                    sqlBulk.DestinationTableName = "imp_master_test";
                    sqlBulk.WriteToServer(dr);

                    excelConnection.Close();

                    File.Delete(path);




                    // To move error files to the error folder



                    /// end


                    T1.Interval = 20000;
                    T1.Enabled = true;
                    T1.Start();

                    T1.Elapsed += new System.Timers.ElapsedEventHandler(T1_Elapsed);
                }
            }
    }


        void T1_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
        {
            T1.Enabled = false;
            try
            {
                SqlConnection strconnection = new SqlConnection();
                strconnection.ConnectionString = @"Data Source=10.91.XXXXXX;Initial Catalog=XXXXX;User ID=XXXXX;Password=XXXXX;";
                strconnection.Open();
                // To get the all files placed at the shared path
                DirectoryInfo directory = new DirectoryInfo(@"D:\Impexp\Data\");
                FileInfo[] files = directory.GetFiles("*.xlsx");



                foreach (var f in files)
                {
                    string path = f.FullName;

                    // TO establish connection to the excel sheet
                    string excelConnectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + path + ";Extended Properties=\"Excel 12.0;HDR=Yes;IMEX=1\";";
                    //Create Connection to Excel work book
                    OleDbConnection excelConnection = new OleDbConnection(excelConnectionString);

                try
                {
                    excelConnection.Open();
                    //Create OleDbCommand to fetch data from Excel
                    OleDbCommand cmd = new OleDbCommand("Select * from [Report$]", excelConnection);

                    DbDataReader dr = cmd.ExecuteReader();
                    // OleDbDataReader dReader;
                    // dReader = cmd.ExecuteReader();
                    SqlBulkCopy sqlBulk = new SqlBulkCopy(strconnection);
                    //Give your Destination table name
                    sqlBulk.DestinationTableName = "imp_master_prod";
                    sqlBulk.WriteToServer(dr);

                    excelConnection.Close();

                    File.Delete(path);



                }
                // To move error files to the error folder
                catch (Exception exp)
                {

                    excelConnection.Close();
                    File.Move(path, Path.Combine(@"D:\Impexp\error\", f.Name));
                    string path1 = @"D:\Impexp\error\error.txt";
                    if (File.Exists(path1))
                    {
                        // Create a file to write to. 
                        using (StreamWriter sw = File.AppendText(path1))
                        {
                            sw.WriteLine("File : " + path + " : " + exp.Message);
                            sw.Flush();

                        }
                    }


                        T1.Enabled = true;
                        T1.Start();

                    }
                }
                strconnection.Close();

            // End of TRY 1

            }
            catch (UnauthorizedAccessException UAEx)
            {
                string path1 = @"D:\Impexp\error\error.txt";
                if (File.Exists(path1))
                {
                    // Create a file to write to. 
                    using (StreamWriter sw = File.AppendText(path1))
                    {
                        sw.WriteLine(UAEx.Message);
                        sw.Flush();

                    }
                }
                T1.Enabled = true;
                T1.Start();
            }
            catch (PathTooLongException PathEx)
            {
                string path1 = @"D:\Impexp\error\error.txt";
                if (File.Exists(path1))
                {
                    // Create a file to write to. 
                    using (StreamWriter sw = File.AppendText(path1))
                    {
                        sw.WriteLine(PathEx.Message);
                        sw.Flush();

                    }
                }
                T1.Enabled = true;
                T1.Start();
            }
            T1.Enabled = true;
            T1.Start();


        }

        protected override void OnStop()
        {
        }
    }
}