Error: Cannot create a user with an empty login name.

Today I was experimenting with switching from Buddypress to UsersWP.

I’ve got WordPress 5.3 and UsersWP 1.2.0.11

I used a plugin called “Export User Data” to export my Buddypress users to a CSV file. Next, I uninstalled Buddypress and all related plugins. I then activated UsersWP, and used the UsersWP option to “Import CSV.”

The import didn’t seem to be a smooth operation because I saw an error (in the UsersWP error notification area) that said:
“Row – 31 Error: Cannot create a user with an empty login name.”
(It was actually multiple errors ie Row – 32, Row – 33, etc, probably 1 for each user.)

I don’t know what is meant by this error description. Can you suggest something based on this info? Or is there more info I can share to shed light on this issue?

Thanks.