I spent 3 hours going thru jacyln’s wordpress site and I have been putting together wordpress site’s for people for YEARS and I don’t see a single problem in the way that she has the plugin installed.
What the problem I think here is a mediocre tutorial that you provide which is outdated to the way that MailChimp is today. The mailchimp embed code is no longer in the bottom right on the form creation page when you create the thank you form.
The problem also lies with MailChimp for creating an unuserfriendly design on their website which really in my opinion makes no sense at all.
From what I see is once the embed code get’s placed into the box it’s supposed to activate the spaces below but it doesn’t. I tried different variations from the code that mailchimp provides and I can’t get it to work. When try clicking the down arrow to open up the dropdown I can see at the bottom where Chrome wants to open up another box but it quickly closes so there’s something going on. I’ve tried it in different browsers, Internet Explorer is blank too.