You are receiving this error message because you have data mapped to the QuickBooks field, Name, and that name does not exist in QuickBooks as either a customer, vendor, employee or another name.
You either need to add this name to QuickBooks pre-import or if you would like Transaction Pro Importer to create the name for you can add the /JE_NAME command line parameter. When you add this command line parameter additional fields to the mapping screen where you can specify the entity type in the Journal Entry “Name” column. In “JE Name Type” specify C for Customer, V for Vendor, E for Employee, O for Other Name.
For more info on how to set this command line parameter please review this article.