Just saw your response....
No, clicking on the minimized window  doesn't do it. I have another
program open  that is "push-pinned" to remain on top. It has 3 windows,
and all must be visible  also. I've left a space  for the Excel window
where nothing touches it, but whenever I select any of the other
windows, such as an order ticket, the Excel window minimizes,
effectively disappearing.