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.

It is possible to create a macro in an Excel sheet that unlock the sheet which is already protected by a password. Users can easily prepare a document in the sheet and then lock it again with a ...

There are several options available to you to protect your Excel file with a password. Remember that once you protect the Excel file, you cannot open it without entering the password.

At the file level, you can password protect an Excel workbook in two ways: You can determine who can get in and who can save changes.

You can add or remove a password from your Excel spreadsheets through the File tab. You'll do it slightly differently on a Mac and PC.