ETL script - 'object' does not contain a definition of 'Value' in Microsoft.Office.Interop

I have a .net 4.5 project getting data from an Excel file and saving some of it to files. It runs perfectly.

However, I decided to make an ETL process of running this script and then uploading it to a database. In the script task of the ETL process I simply paste the same code to the window, add the same references etc and get a bug: 'object' does not contain a definition of 'Value'.

Here's the code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.Office.Interop;
using Excel = Microsoft.Office.Interop.Excel;

namespace etl.csproj
{
        public void Main()
        {
            process();
            Dts.TaskResult = (int)ScriptResults.Success;
        }

        static void process()
        {
            string mySheet = @"C:\\pathToMyExcelFile";
            System.IO.StreamWriter file = new System.IO.StreamWriter(@"C:\my file.txt");
            Excel.Application excelApp = new Excel.Application();
            Excel.Workbook xlWorkBook = excelApp.Workbooks.Open(mySheet, 0, true, 5, "", "", true, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "\t", false, false, 0, true, 1, 0);
            Excel.Sheets sheets = xlWorkBook.Worksheets;
            Excel.Worksheet worksheet;

            for (int i = 1; i < sheets.Count; ++i)
            {
                worksheet = (Excel.Worksheet)sheets.get_Item(i);
                for (int j = 5; j <= 9; ++j)
                {
                    for (int k = 68; k <= 72; k++)
                    {

                        if (worksheet.Cells[k, j].Value2 != null) //HERE IS THE ERROR
                        {
                            file.WriteLine(worksheet.Name + "|" + (string)(worksheet.Cells[k, 2] as Excel.Range).Value /*ERROR HERE*/ + "|" + (j - 4).ToString() + "|" + worksheet.Cells[k, j].Text/*ERROR HERE*/);
                        }
                    }


                }

            }
            file.Close();
        }

    }
}

The only change in those two projects' metadata is that the latter is built in .NET 3.5, not 4.5 (I cannot change the version). I would be grateful for any help!