Zoom Pardot Integration: Submit webinar information via Pardot

Hi there,

my aim is to register participants via a Pardot form to a zoom webinar. All communication should be sent exclusively via Pardot. 

Initially, I created everything as described here: https://support.zoom.us/hc/en-us/articles/206003126-Using-Zoom-Webinars-for-Pardot 

After submitting the Pardot form the participant is registered in the mentioned Pardot list, also I see the registration in Zoom. However, I do expect that the personal link is created in the field webinar_join_link in Pardot. Unfortunately, this field stays empty in Pardot. Anyone an idea?

Thank you really much for your support