CSV User Import – problem with import

(I posted this at the bottom of another thread that seemed resolved and thought I’d start a new topic in the hope of getting help. TIA.)

Andy, I’ve encountered a problem with the plugin. Hope you can please tell me what I may have done to cause it. I had had 705 Subscribers in my WP database (along with 5 admins and 1 editor). After backing up the database (for safekeeping), I delete all subscribers, leaving 6 users. Then I set up a test .csv that had first name, last name, user name, email address. It took a very long time to import the short list of just 10 users, but it said it was successful. But no subscribers were added to the user list.

One thing that concerned me: The WordPress User screen displays:
username, name, email, role.

How do first name and last name fields get combined into the name field?

FYI, since our members were accustomed to using their email addresses for their IDs and only one universal (non-customized) password, we added the field in the csv for the user name to match the email address and the field for the password to contain the universal password.

Would having had separate fields for firstname and lastname have caused the users to not be properly imported?

Thanks for your help!