It could depend on how the CSV file was created...
To have a clue, you can, on the platform, edit a name (where you know there is the issue), and check the fields Name, First Name and email address. There is possibly a space charatcer in one of these fields (I said a clue
If so, please open th eCSV document and check if the space exists... It may!
To create a CSV, we usually use Copy/Past (or Ctrl C, Ctrl V) from a software such as email (Outlook adn so on), this copy can add a space in the fields, you therefore have the issue.
I hope this helps.