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.

This guide will show you how to safely unlock your password-protected documents — including PDFs, Word, and Excel files — using Wondershare Dr.Fone.

Microsoft Office 2010 includes a new "Protected View" that, by default, will open all Outlook attachments and documents downloaded from the Internet in "read-only" mode.