With WPSubscribers version 1.53 a API level support for Mailchimp has been implemented.
the old version was using a copy / paste of a form you were creating with Mailchimp access, it was causing some issues and may be kind of painful for some people.
Mailchimp API lets you have a fine control on your integration. Here is the step by step tutorial
1 ) Get or Create your API key from your mailchimp account
2 ) in WPSubscribers, go to “others settings” and put your API key
3 ) Get your List_id from Mailchimp
Connect to Mailchimp again, click on list and settings
from the list , you will the submenu Settings , then List Settings and Unique ID
you will have a special ID to copy like in this screenshot
3 ) you need to set up your form as usual
in Form Action URL: put exactly this value
If you use WordPress in multisite version use the complete url like http://youblogurl.com/wp-content/plugins/wpsubscribers/mailchimp.php
form name field is FNAME or anything else defined in mailchimp
default is FNAME, refer to the form code to adjust the field values
UPDATE ! depending on your host, you may name to use “email” and not “EMAIL” it's lowercase sensitive
If you have anything, please contact us, or let a comment, and we will adjust it for you.
Important : ADD in hidden fields this line :
<input type="hidden" name="list_id" value="xxxxx">
where you replace xxxxx by your mailchimp list ID