I have CMC 3.0.1 installed in Joomla 3.6.2 with Community Builder 2.0.15. I have entered the API key and webhook. I have the CB plugin installed, enabled and field mapping setup as:
EMAIL=email
FNAME=firstname
LNAME=lastname
Those are correct names from both MC and CB. I also have some additional fields setup to sync some user choices. Those fields show up in the registration form from Mailchimp fine.
I have done the sync in the CMC component also with my Mailchimp list.
When I do a user registration, and confirm the email sent from CB, nothing is added to Mailchimp and no user is added to the list of users in CMC (not sure if it's supposed to). Everything appears to be setup as needed, but it's simply not adding new registrants. What could I be missing potentially?