This error shows up when an item was initially created in QuickBooks, synced with EZR, and then made inactive in QuickBooks. In order to sync again, you will have to mark the item as active again in QuickBooks.
To check if an item is marked as inactive, please apply the following filter in QuickBooks:
In case the item is marked as inactive in QuickBooks, please mark it as active by going to Settings –> Products and Services –> Change Filter from Active to Inactive –> Apply. Click “Mark Active” in the action column for the particular item.