I've successfully gotten my script to add contacts to my lists, but I cannot get them to add to my default list. My default list is #7. I can use every other list ID and it adds it just fine, but when I use list 7 (default list) it says it's a bad list:
Error 400: Contact List id: 'http://api.constantcontact.com/ws/customers/*xxx*/lists/7' does not exist
I would like to help you with the issue you are having when you try to add a contact to your list. The error you are receiving usually only happens when the list you are pulling is not an existing list. The best way to find the list ID for a specific list is to do a GET call on the List collection URI, and the list ID is found under the link element for the specific list.
An example would be "<link href="/ws/customers/joesflowers/lists/2" rel="edit" />"; in this case the List ID is 2. Please note that the List ID is not the same as the Sort order, or the number that you see when you are logged into the user interface in your account.
If you pull the list collection and your default list is 7, and you are still returning an error, we may want to look further into this. If you could please email your username and also the list name that is not working to the webservices support team, and we should be able to help you resolve this issue.