Jetpack won't connect to WordPress

Getting this message when trying to connect:

Jetpack could not contact WordPress.com: register_http_request_failed. This usually means something is incorrectly configured on your web host. Operation timed out after 15005 milliseconds with 0 bytes received.

I see this is a common problem, and I have tried to search for a solution, but I’m a complete noob at this and I’m getting nowhere.

So, some information:

I am hosting via a new Synology Diskstation.
My Site is live, because I can access it via my phone both via Wifi and 3G
I downloaded and ran a ‘check compatibility’ plugin that was mentioned on another thread and this is what it returned (less my URL info):
Site info

SITE_URL: https://*************/wordpress
HOME_URL: https://*************/wordpress

TEST: HTTP Connection
Array
(
[headers] => Array
(
[server] => nginx
[date] => Fri, 03 Jan 2014 16:33:01 GMT
[content-type] => text/plain;charset=utf-8
[connection] => close
[vary] => Cookie
[x-pingback] => https://jetpack.wordpress.com/xmlrpc.php
[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
)

[body] => OK
[response] => Array
(
[code] => 200
[message] => OK
)

[cookies] => Array
(
)

[filename] =>
)

TEST: HTTPS Connection
WP_Error Object
(
[errors] => Array
(
[http_request_failed] => Array
(
[0] => SSL certificate problem: unable to get local issuer certificate
)

)

[error_data] => Array
(
)

)

TEST: Self Connection
Array
(
[headers] => Array
(
[date] => Fri, 03 Jan 2014 16:31:52 GMT
[server] => Apache
[set-cookie] => wfvt_-458540382=52c6e5f8dc270; expires=Fri, 03-Jan-2014 17:01:52 GMT; path=/
[vary] => Accept-Encoding
[content-length] => 42
[connection] => close
[content-type] => text/plain
)

[body] => XML-RPC server accepts POST requests only.
[response] => Array
(
[code] => 200
[message] => OK
)

[cookies] => Array
(
[0] => WP_Http_Cookie Object
(
[name] => wfvt_-458540382
[value] => 52c6e5f8dc270
[expires] => 1388768512
[path] => /
[domain] =>
)

)

[filename] =>
)

There are definitely bits in there that mention errors, so does anyone have any suggestions of what could be wrong?

I've been searching websites and forums for the past 24 hours but to no avail…...