Mailchimp Error

I believe I have configured everything in the plug-in correctly. I’ve connected it via API to my MailChimp account. But whenever I try submitting an email sign up, I always get the following error in the MailChimp log:

The resource submitted could not be validated. For field-specific details, see the ‘errors’ array.

Perhaps there is an error in the actual plugin code? See this StackOverflow thread: https://stackoverflow.com/questions/41508831/mailchimp-api-3-0-invalid-resource-error

The page I need help with: [log in to see the link]