If you see this error code, it means your audience settings has too many required
, so Mailchimp is preventing us from adding new subscribers to your audience.
To resolve this issue, either create a new audience that only requires the email field or edit the current audience to no longer require any additional extra fields.
You can do that on the Mailchimp dashboard
Go into your Mailchimp dashboard
Click "Audience" and select the audience you want to use
On the audience page, click "Manage Audience" then "settings" then you will be on the audience settings page
Now, click the settings menu item called "Audience fields and *|MERGE|* tags"
You will now see a table of all fields, make sure only the email field is marked as required and click "save changes" at the bottom of the screen
Now test the form on your website using a real email address. Once a subscriber passes successfully, the error will be gone.
Audience fields and *|MERGE|* tags
Making sure only Email field is required