Unable to add another field in Mad Mimi integration

Also, I was trying to add another tab for Birthdays outside of just the first name, last name and email and it wouldn't populate.

Upon checking, the integration only supports 3 form fields. The First Name, Last Name and Email address. You may try adding another field inside Mad Mimi Dashboard and then edit the integration again. Here's a screenshot:

Related guide: https://www.jotform.com/help/396-How-to-Integrate-Form-with-Mad-Mimi

Hope that helps. Thank you.