Error Code 9999: Unable to Sync Orders Due to Disabled Inventory Tracking in QuickBooks Online.
Cause:
This error occurs when Inventory Tracking is turned off in QuickBooks Online, while in Webgility, the option to create new inventory-type items is enabled under Sync Settings> Products.
Steps to Resolve the Error:
Enable Inventory Tracking in QuickBooks Online - Please refer to this Set up and track your inventory in QuickBooks Online
In Webgility under Sync Settings>Products>Create a new item in QB and set the new item type is Inventory.
Once inventory tracking is active, go to Webgility and refresh the order sync settings.
Now you should be able to post your orders without an error.
Alternative (Inventory Tracking is Unavailable in Your QBO Plan): If your current QuickBooks Online plan doesn’t support inventory tracking, you have two options.
Upgrade your QuickBooks Online plan to one that includes Inventory Tracking.
Configure Product Sync Settings in Webgility - Sync Settings> Product Sync, Under Create new QuickBooks items set the option to Non-Inventory to avoid requiring inventory tracking.
With these steps, you should be able to resolve the error and sync your orders correctly.
If the issue is still not resolved feel free to reach out to us.