If you record a payment for an invoice, and the balance for the invoice does not update or the payment goes into a sync conflict, the reason may be the invoice may not have synced.
Sync the Invoice Retry Payment Sync
Open up your invoice and uncheck Wait for Sync Approval if checked, then Save.
Open up the associated payment. If it's synced, you're done, however, there's a good chance it has a Sync Conflict.
Open up your Profile icon and select Integrations.
Select QuickBooks Sync.
Select View conflicts.
Click the checkbox that has your ReceivePayment conflict, and then click Retry sync.
Go back to QuickBooks sync, and click Changes only sync.
If you check your payment now, it will be show it has synced.
If payment has not synced
Another sync conflict may be causing the problem.
The sync is disconnected.
Please check your sync connection if you are using QuickBooks Online, or the Method Sync Engine if you are using QuickBooks Desktop.
If there are no conflicts, you can manually start the syncing process, as shown above with the Changes only sync.