The cause appears to be the use of non-ASCII characters in file names. Microsoft describes it like so: “Any user may be ...

Microsoft has started looking into a problem that is preventing users from opening some Excel file attachments with non-ASCII ...

Microsoft is working to resolve a known issue that prevents some users from opening Excel email attachments in the new Outlook client.

If you see the “The file couldn’t open in protected view” error while opening Microsoft Excel, the solutions listed in this post may help you resolve the issue ...

The troubleshooting guidelines to deal with this problem are explained below. But before you proceed, close all the Excel files and open Excel again. Now, check if you can type something in your Excel ...

If you work with multiple Excel files over the course of a workday, and especially if you use a dual-monitor setup, you might wonder how you can launch each Excel file in its own window so you can ...

There is a workaround, though.