Hi @avichopra - Thanks for the tag. The Visitor Identification API should work from the KB, but it sounds like we may need additional specifics to get to the root cause. I recommend reaching out to our support team for next steps in troubleshooting the behavior you are seeing.
Hi @jpw_andy - At this time, the Visitor Identification API will work with any Pro level subscription across any Hub (Marketing, Sales, Service, or CMS) but is not available for an individual upgrade. Thank you for this feedback!