Writing to excel using Open XML

Question

I have written a code to write to an excel file in OpenXML. this works for only one time for the second time, I am getting an error while opening the file as "We found a problem with some content in output.xlsx"

public static void WriteToExcel(string fileName, string SKU_Address, string SKU_Value, string ItemName_Address, string Item_Name_Value)
{
SpreadsheetDocument spreadsheetDocument = SpreadsheetDocument.Open(fileName, true);
// Add a WorkbookPart to the document.
WorkbookPart workbookpart = spreadsheetDocument.WorkbookPart;
// Add a WorksheetPart to the WorkbookPart.
WorksheetPart worksheetPart = workbookpart.WorksheetParts.FirstOrDefault();
Worksheet worksheet = worksheetPart.Worksheet;
SheetData sheetData = worksheetPart.Worksheet.Elements<SheetData>().First();
Row row = new Row();
//intialize a cell and add values to the required cell based on address
Cell cell1 = new Cell()
{
CellReference = SKU_Address,
DataType = CellValues.String,
CellValue = new CellValue(SKU_Value)
};
row.Append(cell1);
//intialize a cell and add values to the required cell based on address
Cell cell2 = new Cell()
{
CellReference = ItemName_Address,
DataType = CellValues.String,
CellValue = new CellValue(Item_Name_Value)
};
row.Append(cell2);
sheetData.Append(row);
worksheetPart.Worksheet.Save();
// Close the document.
spreadsheetDocument.Close();
}

I guess I am missing something somewhere else. please help.