I believe I may have found the underlying issue and I am asking for some help in confirming. 

I think the issue is related to the type of subscription a client has and the way their profile is created. The issue being Simple Start clients are categorized by their first and last name, and Essentials and Advanced are categorized by their business name.

Could someone check to see if the import works for their clients with Essentials and above, but does not work for clients with Simple Start?