I'm unable to map the Key (or Issue Key) field during the import, so instead of updating my new custom field for an existing issue, I get a brand new issue. Key field is not available as a choice to map to from my input file, but it is a column present in my CSV file.
Has anyone solved this before? I have a large number of items that I need to update, and the information is already in a spreadsheet, so I want to take advantage of that.