MailChimp Error Message during Sign-Up

I tried testing the registration process for a new multi-site on my website and I'm getting an error message when I click the link that is emailed to me to activate the new site.
The error is:
"Warning: MailChimp listSubscribe() Error: 200 - Invalid MailChimp List ID: in ...mailchimp-sync/mailchimp-sync.php on line 106"

Any help on what I should do to remove the error message?