Hi,
I’m having a similar problem and your solution makes sense, but whenever I try to copy the correct form action URL into the box on the admin page nothing happens when I click save changes. Nothing has changed when I open a new tab and look at the page with the opt in form on my site. Whenever I try to refresh the admin page the following code is pasted into the box:
<!– Begin MailChimp Signup Form –> <div id=