Unable to register for public webinars with my free Zoom account.

I am unable to register for public webinars with my free zoom account. 

I am trying to join a public webinar hosted by Aurora Energy: 

https://auroraer.zoom.us/webinar/register/1817338665272/WN_Za6zPKuiQEubkfNhvOTW1g#/registration
However, when I enter my registration information, I get an error saying "This webinar is only for authorized people. Register with a different email address". Although the webinar is clearly a public webinar, and the email adress I use for registration has a free zoom account associated with it. 

I have raised this issue with Zoom in several tickets over the last few months, without getting any helpful response. Now my tickets are simply being closed whenever I create them. 

Anyone else has similar problems, or is there anyone with a free zoom account who has actually been able to register for a public webinar?