The Excel file may say it’s locked if the user who shared it with you is currently editing the document. It can also be because the Office app running in the background has already opened the file.

On the right side, select the Open checkboxes for the file types that you want to open in the Protected View. Now, select the Open selected file types in Protected View radio button at the bottom.

At one time, people would share Excel files and other documents by emailing them back and forth or coordinating times to open them on a shared drive. But nowadays, you can use Excel with multiple ...