Why XlsIO throws "cannot recognize current file type" exception?

using Syncfusion.XlsIO;
using System.Collections.Generic;
using System.IO;
using System.Reflection;
 
namespace XlsIO_Sample
{
    class Program
    {
        public static void Main(string[] args)
        {
            //Instantiate the spreadsheet creation engine
            using (ExcelEngine excelEngine = new ExcelEngine())
            {
                IApplication application = excelEngine.Excel;
 
                Assembly assembly = typeof(Program).GetTypeInfo().Assembly;
                Stream fileStream = assembly.GetManifestResourceStream("XlsIO_Sample.Data.xls");
 
                if (application.IsSupported(fileStream))
                {
                   //Open the existing workbook
                    IWorkbook workbook = application.Workbooks.Open(fileStream);
                    IWorksheet worksheet = workbook.Worksheets[0];
 
                    //Save and close the workbook
                    Stream stream = File.Create("Output.xlsx");
                    worksheet.UsedRange.AutofitColumns();
                    workbook.SaveAs(stream);
                }
            }
        }
    }
}
 

Imports Syncfusion.XlsIO
Imports System.Collections.Generic
Imports System.IO
Imports System.Reflection
 
Namespace XlsIO_Sample
 
    Class Program
        Public Shared Sub Main(ByVal args As String())
            'Instantiate the spreadsheet engine
            Using excelEngine As ExcelEngine = New ExcelEngine()
 
                Dim application As IApplication = excelEngine.Excel
                Dim assembly As Assembly = GetType(Program).GetTypeInfo().Assembly
                Dim fileStream As Stream = assembly.GetManifestResourceStream("XlsIO_Sample.Data.xls")
 
                If application.IsSupported(fileStream) Then
                    'Open the existing workbook
                    Dim workbook As IWorkbook = application.Workbooks.Open(fileStream)
                    Dim worksheet As IWorksheet = workbook.Worksheets(0)
 
                    'Save and close the workbook
                    Dim stream As Stream = File.Create("Output.xlsx")
                    worksheet.UsedRange.AutofitColumns()
                    workbook.SaveAs(stream)
                End If
 
            End Using
        End Sub
    End Class
End Namespace