Switch your QuickBooks Online Account to work with Categories
To enable the sync of items from Flourish to QuickBooks Online, please ensure your QuickBooks Online account is configured to work with "Categories" and not "Sub-items."
QuickBooks Online recommends switching to "Categories" to simplify organizing your products and services.
To do that:
Learn more on Categories at the QuickBooks Online help center.
If you don't switch to "Categories," you will get this error message when trying to sync an item to QuickBooks Online: "...Code: 500 | Message: Unsupported Operation | Detail: Operation CREATE CATEGORY is not supported"