I was having the same error (among others like HTTP[403]). Make sure to deactivate all other plugins, there is a known list of known conflicting plugins: https://jetpack.com/support/getting-started-with-jetpack/known-issues/ (Including typical ones like iThemes security, W3 Total cache, WP All Export )
If you use a CDN or Cloudflare it may be worthwhile checking out that help article: http://support.cloudflare.com/hc/en-us/articles/218377098-WordPress-JetPack-and-CloudFlare
Also it seems that for some deactivating, uninstalling, and reinstalling Jetpack helps.
Also check your XMLRPC file. You can do this by going to your web site URL and adding â/xmlrpc.php
â to the end (without the quotes). When it loads in your browser, you should see âXML-RPC server accepts POST requests only.â on a line by itself. Common causes for this, again, are plugins or themes conflicting.
I had tried all of the above and the final thing to let it connect was php.ini configuration changes. Beyond the typical ones like increasing memory:
memory_limit = 512M
upload_max_filesize = 100M
post_max_size = 512M
max_execution_time = 300
max_input_time = 300
... this was the one to fix it:
output_buffering = 2048
I was using HostGator but I have a feeling other shared hosting environments like GoDaddy may have the same issue.
I wrote an article going through all the steps I took beyond that ( http://www.gordowebdesign.com/wordpress-troubleshooting-jetpack-failed-connection-curl-error-28-operation-timed-out-after-1000-milliseconds-with-0-bytes-received-solved/ ). Deactivate all other plugins before going further, and check that list. One of them is most likely the culprit.
Also it is worthwhile to run the debugger and check the output for helpful information:
http://yourdomain.com/wp-admin/admin.php?page=jetpack-debugger
or visit http://jetpack.com/support/debug/
and add your URL.
If this doesnt work make sure to enable define('JETPACK_DEV_DEBUG', true);
in your wp-config.php
(Need more reputation to post those as links, sorry)