Open each Excel workbook as a separate window

[Another Brian]

Until a few days ago, when I opened multiple Excel files, each would
open in its own instance of Excel. In other words, each would have its
own window. If I wanted to arrange multiple spreadsheets, I did not
have to use the Windows + Arrange function. It didn't matter if I
opened the spreadsheets through Windows Explorer or File+Open. How do
I get this ability back?

I few things that I've tried are going to Tools+Options, View tab and
unchecking Windows in Taskbar. That just places one instance of Excel
on the task bar.

Brian