MailChimp App Issues

I'm having issues getting the MailChimp App to work. I've created the following form and it shows up on my website. I can submit it and my success message appears, but my users never receive the confirmation email to confirm their subscription. I have the API connected to the Perch settings and the correct list id and list name in the form (removed from this post for security.)

Any ideas on why this wouldn't be working?

This is what I have configured on the page:

<?php perch_mailchimp_form('forms/subscribe.html'); ?>

This is the form template:

<perch:form id="subscribe" app="perch_mailchimp" double-optin="true"> <perch:input id="email" required="true" type="email" mailer="email" placeholder="Your email address..." required class="toolbox-form--input" /> <perch:error type="required" for="email">Required</perch:error> <perch:input type="submit" value="Submit" class="toolbox-form--submit" /> <perch:input type="hidden" value="1" id="confirm" mailer="confirm_subscribe" /> <perch:input type="hidden" id="list" value="a9599*****" mailer="list" /> <perch:success> <h3 class="success">Thank you for joining our mailing list!</h3> </perch:success> </perch:form>