Headers Already Sent after turning on User Sync

Hello!

I have the MailChimp Auto-Plugin installed that allows users to automatically be added to a list. Once I turned on the User Sync plugin I get this error when trying to register:
Warning: MailChimp listSubscribe() Error: 502 - Invalid Email Address: contact@test.com in /home/content/45/11923645/html/wp-content/plugins/mailchimp-sync/mailchimp-sync.php on line 144

Warning: Cannot modify header information - headers already sent by (output started at /home/content/45/11923645/html/wp-content/plugins/mailchimp-sync/mailchimp-sync.php:144) in /home/content/45/11923645/html/wp-includes/pluggable.php on line 678

Warning: Cannot modify header information - headers already sent by (output started at /home/content/45/11923645/html/wp-content/plugins/mailchimp-sync/mailchimp-sync.php:144) in /home/content/45/11923645/html/wp-includes/pluggable.php on line 679

Warning: Cannot modify header information - headers already sent by (output started at /home/content/45/11923645/html/wp-content/plugins/mailchimp-sync/mailchimp-sync.php:144) in /home/content/45/11923645/html/wp-includes/pluggable.php on line 680

Warning: Cannot modify header information - headers already sent by (output started at /home/content/45/11923645/html/wp-content/plugins/mailchimp-sync/mailchimp-sync.php:144) in /home/content/45/11923645/html/wp-includes/pluggable.php on line 875

any ideas on how to solve this issue??

Regards,

UpcomingMedia