Harish Chouhan on "[Plugin: MailChimp for WordPress] MailChimp API Error"

Hi,
I have created some extra fields in the default user registration form and he registration process works fine.
However, when I activate the Mailchimp for WordPress plug-in, so that new registrants are added to my Mailchimp list, one field is being rejected by the Mailchimp API.

Debug Log
[2016-07-09 16:49:54] ERROR: Registration Form > MailChimp API Error: MMERGE9 must be provided - Please enter a value

Form Field Info
Name: MC4WP-MMERGE9
Type: Dropdown
Label: Business Type/ Consumer, Retailer, Hospitality, Marketing, Wine Trade, Producer, Media/Publication, Other
(includes dropdown options)

Mailchimp Field Info
Name: MMERGE9
Type: Dropdown
Label: Business Type
Business Type Options: Consumer, Retailer, Hospitality, Marketing, Wine Trade, Producer, Media/Publication, Other

Any advice gratefully received!

Colin Ford
http://www.winework.com

https://wordpress.org/plugins/mailchimp-for-wp/