This error is typically related to the shipping setting being disabled in QuickBooks while trying to sync an invoice with shipping costs added.
Double check if the shipping setting is on in QuickBooks by following these steps:
1. Click on the Gear icon.
2. Select Accounts and Settings.
3. Select Sales.
4. Refer to the Sales form content and make sure that the Shipping box is checked.
Here's a screenshot:
Once it's "On" -- please click 'Retry' for this specific invoice from within your DesignFiles project.
This should resolve this particular error.
If you have followed all the steps and you are still experiencing the same sync error, please contact us via the Chat Bubble in the bottom right.