QuickBooks has recently introduced a new message which is displayed depending on your Sales settings.
This prevents Syngency from updating an invoice or bill, if a payment has already been added to it.
If you want to override this behaviour, follow these steps:
- Click the Settings icon in the top-right corner of your QuickBooks screen
- Under Company Settings > Sales > Sales Form Content, find the checkbox labelled Deposit.
- Make sure the Deposit checkbox is checked.
- Click Save..
Now Syngency is able to update invoices and bills that have already had payments assigned to them.