Message: SEVERE: There are # DUPLICATE ENTRIES for Customer: {BILL FIRST NAME BILL LAST NAME} - Enter Order Manually
Explanation: The Customer Match settings that you have selected on import, there are still multiple customer records available to merge with.
Suggested Resolution: Select Customer Match criteria that is more specific.
Special Considerations: Regularly running a Customer Dedupe in your instance will merge multiple customer records existing for the same customer, which will potentially eliminate this scenario.