I used the code example off of (Open XML SDK) website and it opens the file and reads the data but returns back values but they are not the values in the cells. I've attached my code and a link to a sample xlsx file.
https://file-examples.com/wp-content/uploads/2017/02/file_example_XLSX_10.xlsx
Private Sub ReadExcelFileDOM(ByVal fileName As String)
Using spreadsheetDocument As SpreadsheetDocument = SpreadsheetDocument.Open(fileName, False)
Dim workbookPart As WorkbookPart = spreadsheetDocument.WorkbookPart
Dim worksheetPart As WorksheetPart = workbookPart.WorksheetParts.First()
Dim sheetData As SheetData = worksheetPart.Worksheet.Elements(Of SheetData)().First()
Dim text As String
For Each r As Row In sheetData.Elements(Of Row)()
For Each c As Cell In r.Elements(Of Cell)()
text = c.CellValue.Text
Console.Write(text & " ")
Next
Next
Console.WriteLine()
Console.ReadKey()
End Using
End Sub