I had the same error.
Contacted my hosting, they wrote:
“We are sorry to keep you waiting, based on the link, it uses curl, however, we would need more details so ask from you and it is better to contact mailchimp support and ask to which port you are using when connecting to your api.”
Mailchimp support said:
I would recommend that you reach out to the developers of that integration as this wasn’t created by Mailchimp so we’re going to be limited in how much further we can troubleshoot from here since we didn’t create the integration.
