Why is the Manage List button missing from the membership component?

On the Mailchimp Memberships component that can be added to lightning pages, the manage list button lets you add and remove any email address on the record to any of your audiences. 

If the button is missing, that means the component can't find any email on the object where you have the component. There are two reasons this may be true:

• The user doesn't have at least Read access to any email fields.
• The object doesn't have a field of data type Email (if a custom object).

To correct, please grant access and/or add the appropriate field. An email field is required for the integration, as Mailchimp uses the email for matching and a unique identifier.