Keep getting this error when pushing WooCommerce orders to QuickBooks Online using MyWorks Sync?

Error

Error:6520: [Missing Inventory Item Quantity, Quantity required for inventory item]

Cause

You have an inventory product selected in MyWorks Sync > Settings > Defaults for Default QBO Coupon Code Product and Default QBO Shipping Product. QuickBooks Online won't accept inventory products for these line items, as they aren't synced to QuickBooks Online with a quantity in the invoice line item.

Resolution

You should have a generic non-inventory product set for both of these settings. We recommend a product named "Shipping" and a product called "Coupon" or "Discount."