MESSAGE

"This key is already associated with an element of this collection (Error #457)"

RESOLUTION

Check the import file to see if there are extra spaces in the list name (Customer, Vendor, Employee, or Item) that is being added. 

The issue is most likely caused by the scenario below:

Customer name in the import file is RIGHT  WAY CLEANERS (note the extra space between the first and second word).

Customer already exists in QuickBooks (QB) as RIGHT WAY CLEANERS.

When Rightworks Transaction Pro Importer goes to look for the Customer in QB, Importer does not find the Customer name in the import file in QB because of the extra space.

Therefore, Importer then tries to add the Customer. The problem occurs because QB strips the extra spaces when adding a new Customer. 

Therefore, remove any extra spaces from the import file and retry the import.