If you Mailchimp form is not working and leads to a 404 page please check the folllowing
- Check you’ve entered your API key in Mailchimp for WP
- In Mailchimp for WP > Forms > Settings make sure that if you filled the “Redirect to URL after successful sign-ups” it goes to a page that exists or is just left empty
- Just in case the demo didn’t import the form correctly, here is what we can try: replace the code in your Mailchimp form by this one (the initial Demo code):
<input type="text" name="NAME" placeholder="Your name" required />
<input type="email" name="email" placeholder="Your email address" required />
<input type="submit" value="Sign up" />
Finally if nothing has worked, review this documentation and make sure that in Mailchimp itself you are not trying to do it (redirect toward a thank you page after submission). That would cause the “Page not found” problem.
This article might also help you with that.