oops. Something went wrong. Try again later.

When I deactivated, Use double enrollment? In your plugin
And deactivated Enable Double opt-in in mailchimp itself
I get the oops. Something went wrong. Try again later. When I add an e-mailadress into the sign-up form on my site.
See: https://ibb.co/Yy38n0Q

How do i fix this?
I do not want the customer to receive a mail with a button to confirm his registration.
I want him to be directly registered when He leaves his email on the sites sign up form.