Every time I try to create a new campaign and I am asked to insert the API code, it shows that message.
I just tried now again and it’s the same.
I believe I might be doing something wrong, then.
I have two lists in my MailChimp account.
Would you mind providing a video recording of how we can reproduce it? You may provide it in private reply. You may also contact Mailchimp support, we can’t fully support it since it’s not our system 🙂 Unless the error appears on your site due to X’s plugin issue.