Hello JenWP,
Lets see how we can help.
I ran a quick test and was able to connect fine. I also don’t have any other users with this issue right now. That means something about your site is preventing us from getting through to MailChimp.
In these cases it’s usually a conflict. But first please try resetting your Mailchimp API key, and trying again with the new one.
If that does not help we will need to check for any conflicts. To search for conflicts, please follow these steps.
1. First please deactivate all plugins except Landing Page Cat and see if the issue persists.
2. If the issue is resolved, reactivate your plugins one by one, testing after each to see if the issue returns.
3. If no conflict is found among your plugins, try reverting to a default WP theme like ‘Twenty Sixteen’, or ‘Twenty Seventeen’, and see if the issue is resolved.
Head here for detailed instructions:
https://fatcatapps.com/knowledge-base/search-for-conflicts/
Let us know your results, and if a conflict is found, with what. We will see what we can do from there.
Thanks,