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.

The error message says that Microsoft Excel cannot open the selected file in Protected View. Therefore, if you disable the Protected View in Trust Center settings, the error may get fixed.

Pro Microsoft Excel is making a major change around blocked file types - here's what we know News By Craig Hale published August 1, 2025 ...