I am trying to use a form built in Elementor (I've also been trying it with Gravity Forms) to create an opt-in form for one of my lists in Zoho Campaigns. 

I've generated a form in Zoho Campaigns and gotten the raw HTML. This HTML form does work fine. 

What isn't working is...

I'm trying to pass the FIRSTNAME and CONTACT_EMAIL fields along with the hidden fields from the raw HTML to  https://publ.maillist-manage.com/weboptin.zc using a webhook in the form builder. The webhook is set to use the POST method. 

However, this does not work. 

Ultimately, what I'm trying to accomplish is to use a form builder like Gravity Forms or Elementor to create my opt-in forms. (The Zoho Forms are just too limited in their design)

Any suggestions?

Thanks,

Scott