I have correctly setup mailchimp integration. ie. I have the API key generated and saved in S2, plus I have added the list ID.
I have created a pro form for free registration. However, when I test the pro form with a free user registration that user is not added to my email list.
How can I troubleshoot this?
Hi Andrew.
The Mailchimp API changed recently and s2Member hasn’t been updated for it yet. Having said that, I want to make sure first that it’s not some other problem you’re having
Could you enable logging and see what the log entries say, or if they mention any problems? WP Admin > s2Member > Log Files
I look forward to your reply. 
Here is the attached log. I am not sure if there is anything strange. It does mention an invalid API key, however I created one in Mailchimp.
Thanks for the log. Yeah, I see that message there too. Did you enter your MailChimp API in the s2Member configuration? WP Admin > s2Member > List Servers > MailChimp > API Key
Yes, I created a new API key in mailchimp called S2 and the pasted it into S2 member list server mailchimp API key.
Am I to assume that the API integration is broken now that Mailchimp has made changes?
Do you have any idea how long it will take to release an update of S2 member that addresses this issue?
I was studying the integration and what it takes to update it to the latest API, but then noticed that the API being used by s2 is still valid, they shut down an older one. So the problem you’re having is not coming from that. MailChimp integration now dead...MailChimp dropped V1.3 API support
There must be something else going on… Could you try the advice from this article? https://s2member.com/kb-article/common-troubleshooting-tips/ (you can ignore the MySQL warning in the Server Scanner)
I look forward to your update.
I found the problem, double optin, people need to verify their email address.
Thanks for your help.
Thanks for the update.