error message on subscription with mailpoet3

I”ve an error message who display on this website https://sweetkwisine.com/ (right widget column) when people subscribe to our newsletter

“Quelque chose s’est mal passé avec votre abonnement. Veuillez contacter le propriétaire du site.”

“Some chose went wrong with your subscription. Please contact the site owner.”

But email are anyway registered on the list… :-/
I desactivate Captcha >> same result.

Thanks for you help

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