Via the API I'm able to create a contact, and add the contact to a list. In CC the list is set to Autorespond to anyone who is added, yet the contact I've added via the API doesn't receive the campaign emails. Is there something I'm missing?
There are two ways you could have set this up in your Constant Contact account and two ways it could be set up with the API call.
Lets start with what is in your Constant Contact account. Are you using an Autoresponder or a Welcome Email? They are both set up in the same area, but they have a different name. If you are using an Autoresponder and it is set up to deliver immediately and the email is not sending then I suggest to call in to our support department at 866-289-2101.
If you are using a Welcome Email you need to make sure you are adding contacts to a list that does not also have an Autoresponder attached to it; Constant Contact will not send both a Welcome Email and Autoresponder to the same list as that can be considered too many emails to one contact.
If you are using a Welcome Email and your contacts are going to a list without an Autoresponder then we need to look at how you have your API calls set up. There is a parameter that can be set to either ACTION_BY_OWNER or ACTION_BY_VISITOR. You will need to use ACTION_BY_VISITOR which tells our system that the contact is signing up on their own. This triggers the Welcome Email to send. Please check the documentation here in the section "Creating a new contact."