Why the Sync Error occurs
This error occurs when an account or customer on an invoice payment or the invoice itself that the payment is attempting to sync to has been deleted in QuickBooks Online (QBO). Without the account, customer, or invoice, the payment cannot sync.
How to Fix the Sync Error
- In QBO, verify that the account or customer listed on the payment has been deleted or determine if the invoice was deleted
- Once the deleted entity is located, reactivate it
- Sync again