Broken connection with MailChimp

Hello,

I successfully connected my Mailchimp account with my API Key and began to use the plugin (version 1.3.1). Love it. But, at the beginning of the week, my Mailchimp connection suddenly broke. And I can’t reconnect it, even with another API Key, I always have this message :
“Oups ! Une erreur s’est produite avec votre fournisseur d’e-mails. Voici le message que nous avons re?u :”
… but without an error.
I don’t understand the matter, am I the only one ?
Thanks fo your help.