ConnectBooks tried to add a record to QuickBooks, but QuickBooks already has one with that name.
How to fix it
In QuickBooks, find the record with that name.
If it's the record ConnectBooks should use, make sure it's active and set up correctly.
If it's a different record, rename it.
Send the settlement again. In ConnectBooks, go to Accounting Export. Click the 3 dots on the settlement and choose "Resend to QuickBooks". If you see Settlement, COGS and Both, pick the one that shows the error.
On QuickBooks Desktop, also run the Web Connector: in QuickBooks, click File, then Update Web Services. Tick your company and click Update Selected.
Frequently asked questions
QuickBooks has 2 records with the same name.
If they're the same thing, merge them in QuickBooks, then send the settlement again.