Is it a basic or a computed column? Computed column cannot be exported in a CSV.
Update : I was wrong.
My bad, you are right. I was looking at my app that does it and forgot that I had to change the selected columns. LOL Thanks @Hassan_Nadeem
@MaximeBaker, computed columns can be exported to CSV.
@Rupert_Wood, are you trying to export multiple-file column? If yes, then that can not be exported to CSV as it’s an Array column. You can use a Join List column to combine all the file links, and use that to export.