Was this meant to be a document or an excel file?
You could reconfirm the file extension. If it is a document, it should be a (.doc) or (.docx) and not (.do).
Or if it is an excel file, the file extension should be displayed as (.xls) or (.xlsx)
Edit: Simply rename the file as "index.doc" or "index.xls" (if applicable)
I hope this helps!
@NickF As I've mentioned, it's a link from an email, and it automatically opens up in Microsoft Word. I can't reconfirm/rename or do anything with the link/file.
@Supernovaa I hear you.
Does the link allow you to download the file? Or do a 'right-click > save as'?
I did some googling and I found the following:
Apparently, the common solution recommended in the link above was to rename the file from (.do) to (.pdf).
Or, you could try opening the downloaded file with Adobe reader or a pdf reader of your choice.
Try and see if it helps?
@Supernovaa Will drop you a PM.