Notification when someone is in a file

Didn't excel used to notify you when entering a file that someone else is editing it?  It would give you the option to enter the file as "Read Only" or "Notify when available."  We have a file that everyone in our office edits at various times.  Currently it doesn't notify you when someone else is in the file.  Therefore, if two people are editing the file at the same time, someone is not able to save their work.  It gives you the option to overwrite the file or you can't save your changes.  I have looked into "Sharing" but I don't think that is what we want.  I am using Excel 365.  I also saved it as "Suggest Read Only" but that is not what I want either.  Any suggestions?