I used the Prime template to add several users.Prime keeps telling me it doesn't recognize the manager email, but it is the manager email in Prime. The system won't recognize that column, so I added another column, and it errors out.
Please use the sample csv file to create your own CSV file and see if this works : Can I add users in bulk? How? | Adobe Captivate Prime Help
Also make sure that all the email IDs in your CSV are in lower case and then try again.
Let me know if this works.
Also make sure that the manager which you are trying to add should be in CSV as well.