This error maybe occur in accounting if  user have a credit memo in QBO with the same transaction number as the invoice.
To Resolve the error user can try one of the three options.
Option 1 : You may need to change the credit memo in QBO to have a different transaction number so that you can  import the invoice.  
Option 2: Cancel the invoice in SB and then create a new one as it would have a different number
Option 3: Change setting in QBO allowing duplicate transaction numbers
Link to QBO Article to enable duplicate transaction number: https://quickbooks.intuit.com/learn-support/en-us/reports-and-accounting/duplicate-invoice-numbers/00/187161