WordPress gives this error when UsersWP tries to create a user from a CSV row that has no username. When it shows for every row, the CSV does not use the column names UsersWP expects, so the username is never found. This happens a lot with files exported from BuddyPress or other user plugins.

Use the column names from a UsersWP export

1. Go to UsersWP > Import/Export > Users and export your users. If the site only has your admin account, that is enough.
2. Open the exported CSV in a spreadsheet. Keep its header row and paste your own users underneath. The username goes in the username column and the email address in the email column. Headings are lower case.
3. Rename or delete columns from your old file that do not match a heading in the export.
4. Save the file as CSV (UTF-8) and import it on the same screen.

How the import treats each row

• If the username or the email address already belongs to an account, UsersWP does not create a second one. It saves the row’s profile columns to that user.
• New users get a random password. Ask them to set their own with the lost password link.
• Only standard columns are imported, such as username, email, first_name, last_name, display_name, bio, phone and user_url. Other columns, including most custom fields from the form builder, are skipped.

Problem rows are reported one by one as “Row – 31 Error: …”. Fix those rows and run the import again. Users that were already created are matched by username or email, so they are not duplicated.

For the import screen and its options, see Settings Overview for UsersWP > Import/Export > Users.