register_http_request_failed

I’ve this message when I try to connect jetpack to my wordpress.com account :
SELF:
Array
(
[headers] => Array
(
[server] => nginx
[date] => Sat, 28 Nov 2015 17:44:23 GMT
[content-type] => text/plain;charset=utf-8
[connection] => close
[expires] => Wed, 11 Jan 1984 05:00:00 GMT
[cache-control] => no-cache, must-revalidate, max-age=60
[pragma] => no-cache
[x-hacker] => Jetpack Test
[x-ac] => 3.fra _dfw
)

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

[cookies] => Array
(
)

[filename] =>
)

Can someone help me please ?
Thank you.