Interesting, works on my end but I'll admit its slightly weird.

It should automatically make a POST to mailchimp and and open a new page showing your successful email list subscription.

I'd be curious what is happening in your network tab or if the navigation to the mailchimp success page is disabled somehow.

Let me know your browser and system anyway, would be much appreciated! Thanks for looking nonetheless!

I don't even see the form on my phone. I suspect I'm just blocking Mailchimp outright. On desktop I see the form.