The receipt in questions is not attached to a customer, or the customer it is attached to has either been deleted or modified.
Check the receipts for this date for ones marked as having not transferred to QuickBooks. Confirm that the customer attached is still listed as a customer in KC and QB and that the customer information is the same in both programs.
If the customer is active in KC and matches the QB information, contact support for more assistance. Support@SoftwareConnectionLLC.com or 1-888-486-4343 option 2.