This is an error, occurring as a result of two actions.
These actions are:
- Deleting a supplier or category in QuickBooks while the items were publishing.
- Disabling the integration with QuickBooks and enabling it again later.
The fix is easy – simply ‘Reload all lists‘. This option is found in the Lists menu -> Categories and then the reload all lists button is found on the top right of the page.
However, if you have disabled your integration the information about your payment methods will be lost and will have to link your bank accounts again.