How to make Finder show icon thumbnail for some Excel documents? I have two Microsoft Excel documents that are, except for the data contained within, virtually identical. One was created as an offshoot of the other. In the Finder, the original displays a thumbnail for the icon but the offshoot copy displays the standard Excel icon with the (XLSX) "button" in the lower left corner.

I've tried:


"Save As" and giving the file a different name. That didn't work.
Checking Get Info on both and the only anomaly I see is that the offshoot is a larger file, despite containing fewer tabs and less data.


How to make the Finder show the icon thumbnail for all Excel documents?
The document filename doesn't matter as much as its extension. Usually .xls or .xlsx will preview OK where comma separated values, tab delimited documents, or something other "spreadsheet" format, which are really just text files rendered in Excel or Numbers, may not preview the way you expect in the Finder.