"This happens when the email list is incorrectly mapped. Please download the email list template and add the respective details in respective columns without adding or editing the header or any column header.
Once the template is created then re-upload it with toggle on with Skip first-line option (mandatory). This will maps the respective fields correctly. This should upload the email list correctly. Also, you may check the mapping window if all the details are properly mapped. You may then use this email list to send out the survey.
Mapping Window screenshot: https://app.screencast.com/y5SlTKOxZ984q
Screenshot: https://www.screencast.com/t/cVwQjRH5
Helpfile: https://www.questionpro.com/help/manage-email-list.html