What can sometimes help if you are having issues uploading a file is to Copy the contents of the file, and paste just the values into a new spreadsheet. From there you can save the file as a CSV (Comma delimited) file and try re-uploading it. If you are still having trouble uploading the file you can send it to us to take a look. Please send the file attached to an email to social_support(at)constantcontact(dot)com with your username and a reference to this post.
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