Error with mailchimp/newsletter component

Hello

When someone tries to signup to my newsletter (from the home page or any other place that uses that block) they get:

There was an error subscribing your email address. Please try again. Error: 400: Your merge fields were invalid.

I tried it as well and getting the same error, whenever the email is not in my mailcjimp list i get this error, if the email exists in the list then it works fine.

Thanks