1) PHP version where Sendy is hosted 7.2
2) Issue occurs when we click on subscribe button. (Button to add a user to the mailing list)
3) In the Sendy library file there is a post request used to post the data to subscribe the user to a particular mailing list
// API which gives error
$this->sendyUrl . '/subscribe'
// Post request which gives error "Unable to decrypt string with openssl_decrypt()"
$return = $http->post($this->subscribeUrl, $data);
The library file path