Save as has the wrong extension when opening a 'XLTM' file or when opening a 'XLSM' through Microsoft.Office.Interop.Excel Workbook.Add()

[giohermans]

Your Environment

• Platform [PC desktop, Mac, iOS, Office on the web]: PC Desktop
• Host [Excel, Word, PowerPoint, etc.]: Excel
• Office version number: Version 2402
• Operating System: WIN11

Expected behavior

When adding a 'XLSM' through _application.Workbooks.Add(path) when going to File -> Save as the extension 'XLSX' shows. The same happens when opening a 'XLTM' file and going to File -> Save as the extension 'XLSX' shows.

Current behavior

When opening any 'XLTM' or the 'XLSM' through the method i would expect to have the 'XLSM' extension pre selected instead of the default 'XLSX'.

When it's a new file and using the CTRL + S shortcut it does have the correct extension preselected.

Steps to reproduce

1. Create a macro enabled template with the 'XLTM' extension.

2. Open the Template by double clicking it.

3. Enable content
   of the document.

4. Go to File -> Save as and see the extension that is selected.

5. Create a macro enabled excel file with the 'XLSM' extension

6. Add the file with _application.Workbooks.Add(path)

7. Open the new Excel file in your application.

8. Go to File -> Save as and see the extension that is selected.

Useful logs

[microsoft-github-policy-service]

Thank you for letting us know about this issue. We will take a look shortly. Thanks.