If you have seen this error message when tying to select a CSV file to upload, there is an easy way to fix the problem.

This error message indicates that there is an issue within the CSV file. To fix the file, open it and scroll to the right to make sure that no additional data has been added (see example below).

If data is not in the relevant columns, this will cause the CSV file to be marked invalid. Make sure that all your data is contained to the cells with appropriate column headers and then save the file and reupload.