We are accessing the box to collaborate on an excel file. The only option we have to open and edit the file is a 'Open' the file - we get this option:

When we open in this manner - we can edit and save but a new file gets saved into the box. My co-workers have the option to open with Microsoft Excel Online but I don't see it. However, I do remember a time that I had that option.
What am I doing wrong?