Marketo Webinar Registrants Not Appearing in Zoom

I've created a webinar program in Marketo that is integrated with a Zoom Webinar, but when I test it, the person that has filled out the form and has been set to registered in Marketo is not appearing as a registrant on the Zoom Webinar. I have it set up so that I have to manually approve registration in Zoom, but I'm not sure that it's related. Does anyone know of a solution?