Please ensure the .xls file is not opened in other workbooks, add-ins, or apps. After coming to that conclusion, simply attempt to open the file again in Excel to see if the problem no longer exists.

If you see The file couldn't open in protected view error while opening Microsoft Excel, the fixes listed in this post will help you.

File-security limits can curtail your ability to open or save Microsoft Excel files.

Microsoft has announced that it will start disabling external workbook links to blocked file types by default between October 2025 and July 2026.