"code": "InvitationOnly",
	"target": "Unknown",
	"details": [
		"code": "InvitationOnly",
		"number": 602,
		"message": "The user or host is not whitelisted to use this API",
		"description": "This API is available to specially invited partners and developers only.  Please contact your business development representative.  Feature: -0- Action: -1-",
		"faultCode": "Client",
		"helpLink": "",
		"severity": "Error"

This indicates that you attempted to contact an API that is available by invitation only. Some AvaTax APIs, such as Returns-related and Onboarding-related APIs, are available to specially approved partners only.

For more information about these APIs, please contact your account manager.