How to insert rows into existing excel files using OpenXmlSDK?

Question

excel

I'm trying to insert a string into a '*.xlsx' file using the OpenXml SDK.
My code:

using var document = SpreadsheetDocument.Open("dspreadsheet.xlsx", true);
    WorksheetPart worksheetPart = document.WorkbookPart.WorksheetParts.First();
    var sheetData = worksheetPart.Worksheet.Elements<SheetData>().First();
    InsertRow(sheetData, 5);
    worksheetPart.Worksheet.Save();


    static void InsertRow(SheetData sheetData, uint rowIndex)
    {
        Row row = new Row();    
                  
        Cell newCell = new Cell { DataType = CellValues.InlineString };            
        var inlineString = new InlineString();
        var text = new Text { Text = "some text for cell" };
        inlineString.Append(text);
        newCell.AppendChild(inlineString);
        row.AppendChild(newCell);        
                             
        var retRow = sheetData.Elements<Row>().ElementAt((int)rowIndex);    
        sheetData.InsertAfter(row, retRow);        
    }

I want to add a new line after the 5th line. But when I open the generated file in Excel 2016, the added row is not there.
Maybe someone knows how to correctly insert lines into existing .xlsx files? Thanks in advance!