Membership 2 Mailchimp addon PHP fatal error


I've just tried to add the Membership 2 Mailchimp addon but when trying to access the settings for it I see the following error instead of its settings:

Fatal error: Uncaught Error: Cannot use object of type WP_Error as array in /var/www/vhosts/ Stack trace: #0 /var/www/vhosts/ M2_Mailchimp->_request('GET', 'lists', Array) #1 /var/www/vhosts/ M2_Mailchimp->_get('lists', Array) #2 /var/www/vhosts/ M2_Mailchimp->get_lists(25, 0) #3 /var/www/vhosts/ MS_Addon_Mailchimp::get_mail_lists() #4 /var/www/vhosts/ in /var/www/vhosts/ on line 61