I have created 3 new lists in my account.
I can see these 3 lists by using Mashery API interface.
When I used same credentials to fetch lists via API from my website; I got the default list "General Interests" only and not the 3 I have created.
Could you please confirm my account settings if I missed anything to configure?
If this is happening in your website, I would suspect that it is possible that you are connected to the wrong Constant Contact account. In order to make sure you are connected to the correct account, I would double-check that your website is using the correct Access Token by re-entering it with the token that you get from Mashery's I/O Docs.
Please let me know if this does not resolve your issue.