Pardot form posting to Zoom webinars directly

Can't find the exact "location" to post this.

Question - Ran into 403 error when posting a pardot / SF Account engagement form for webinar registration via a hidden form with webinarId and posting URL as recommended on the guide https://support.zoom.com/hc/en/article?id=zm_kb&sysparm_article=KB0068276

Pardot captures the registrant correctly but zoom throws the 403 error. Integration/OAuth with SF-Pardot is all working as intended.

Has anyone encountered similar, and how have you resolved it? 

Thank you