I'm deeply sorry for the inconvenience caused to you.
Are these protected worksheets stored on local computer?
Other users on Q&A forum have reported the same issue, that after upgrading to Windows 11 24h2, after double-clicking some workbooks, they cannot be opened via MSI versions of Excel 2016. To let the voice of this issue louder, I suggest you send feedback on this issue to Microsoft with the Feedback Hub app.
Thanks for your understanding.
Currently, the workarounds you can try including:
- Open Excel application first, browsing Excel files, open them within Excel app.
- Turn on the Preview feature in Windows File Explorer. Wait for a popup with a password from Excel shown in the side bar, then open the spreadsheet check whether it shows up the password prompt.
- Back up important data and roll back Windows to 23H2.
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