Problems sending out Emails to email subscribers

Hiya, we have this problem sending out Emails to email subscribers.

Website: https://www.eethetbeter.nl

Now we found: https://eethetbeter.nl/wp-admin/admin.php?page=jetpack-debugger
That says “There seems to be a problem with the ability of the site to communicate with Jetpack.”

We checked:

– The known issues, none of them seem to apply to this website
– Disabled all plugins except Jetpack (did not help)
– The theme, we use DIVI by Elegant themes, i dont think that one is the problem
– Checked the XMLRPC, seems to work ok

We checked https://jetpack.com/support/debug/

– But this gives an “unknown error”

What can you guys do to help us? How do we get this fixed?

Kind Regards,
Ralph

At the debug mode in the website itself, we get the error-log below:

SELF:
	Array
(
    [headers] => Requests_Utility_CaseInsensitiveDictionary Object
        (
            [data:protected] => Array
                (
                    [server] => nginx
                    [date] => Tue, 20 Sep 2016 06:57:25 GMT
                    [content-type] => text/plain;charset=utf-8
                    [expires] => Wed, 11 Jan 1984 05:00:00 GMT
                    [cache-control] => no-cache, must-revalidate, max-age=60
                    [x-hacker] => Jetpack Test
                    [x-ac] => 3.ams _dfw
                    [strict-transport-security] => max-age=15552000
                )

        )

    [body] => {"error":"Unknown Error","error_description":"An unknown error has occurred."}
    [response] => Array
        (
            [code] => 400
            [message] => Bad Request
        )

    [cookies] => Array
        (
        )

    [filename] => 
    [http_response] => WP_HTTP_Requests_Response Object
        (
            [response:protected] => Requests_Response Object
                (
                    [body] => {"error":"Unknown Error","error_description":"An unknown error has occurred."}
                    [raw] => HTTP/1.1 400 Bad Request
Server: nginx
Date: Tue, 20 Sep 2016 06:57:25 GMT
Content-Type: text/plain;charset=utf-8
Transfer-Encoding: chunked
Connection: close
Expires: Wed, 11 Jan 1984 05:00:00 GMT
Cache-Control: no-cache, must-revalidate, max-age=60
X-hacker: Jetpack Test
X-ac: 3.ams _dfw
Strict-Transport-Security: max-age=15552000

{"error":"Unknown Error","error_description":"An unknown error has occurred."}
                    [headers] => Requests_Response_Headers Object
                        (
                            [data:protected] => Array
                                (
                                    [server] => Array
                                        (
                                            [0] => nginx
                                        )

                                    [date] => Array
                                        (
                                            [0] => Tue, 20 Sep 2016 06:57:25 GMT
                                        )

                                    [content-type] => Array
                                        (
                                            [0] => text/plain;charset=utf-8
                                        )

                                    [expires] => Array
                                        (
                                            [0] => Wed, 11 Jan 1984 05:00:00 GMT
                                        )

                                    [cache-control] => Array
                                        (
                                            [0] => no-cache, must-revalidate, max-age=60
                                        )

                                    [x-hacker] => Array
                                        (
                                            [0] => Jetpack Test
                                        )

                                    [x-ac] => Array
                                        (
                                            [0] => 3.ams _dfw
                                        )

                                    [strict-transport-security] => Array
                                        (
                                            [0] => max-age=15552000
                                        )

                                )

                        )

                    [status_code] => 400
                    [protocol_version] => 1.1
                    [success] => 
                    [redirects] => 0
                    [url] => https://jetpack.wordpress.com/jetpack.testsite/1/?url=https://eethetbeter.nl/xmlrpc.php
                    [history] => Array
                        (
                        )

                    [cookies] => Requests_Cookie_Jar Object
                        (
                            [cookies:protected] => Array
                                (
                                )

                        )

                )

            [filename:protected] => 
            [data] => 
            [headers] => 
            [status] => 
        )

)