Mailchimp not tagging new subscribers in dev site

Hi all,

We are trying to implement the Mailchimp add-on to our dev site to tag new subscribers on our mailing list.

The add-on seemed to create the new tag just fine, however it is not actually tagging the new subscribers.

Our freelance developer said that this may be because this is done our our dev site instead of our production site.

We would appreciate any insight on this issue.

Thank you very much!