I have a very strange situation. I have a Excel 97 (.xls) upload in 2 different libraries. One library is in PROD and one library is in TEST. I can preview .xlsx without any problem. The problem is not to be able to preview xls (office 97) but it has to do with how to error message is displayed.
In PROD: I get "We don't know what happened, but something went wrong." and only provides "OK" button.
In TEST: I get "we couldn't open this workbook in the browser" and provides "Open in Excel" and "Cancel" button.
I like how TEST farm is handling the error. What do I need to do in PROD to make it behave like TEST. As far as I remember they were both setup exactly same way.