I am getting this error when entering a new user. Warning:

I am getting this error when entering a new user.

Warning: MailChimp listSubscribe() Error: 200 - Invalid MailChimp List ID: in /home/content/13/10551713/html/wp-content/plugins/mailchimp-sync/mailchimp-sync.php on line 107

Warning: Cannot modify header information - headers already sent by (output started at /home/content/13/10551713/html/wp-content/plugins/mailchimp-sync/mailchimp-sync.php:107) in /home/content/13/10551713/html/wp-includes/pluggable.php on line 878