Error Details: The Jetpack server was unable to communicate with your site [IXR -32300: transport error: http_request_failed Couldn't resolve host 'example.com']
This typically means that you are trying to connect Jetpack too soon after registering a new domain or making changes to your DNS. In both cases, you must allow at least 24 to 72 hours between your changes and when you try to connect Jetpack. If you are still having this error after 72 hours, check your URL at http://whois.domaintools.com/ and make sure that only the proper Name Servers are listed. If your old Name Servers are listed, log in to your DNS manager and remove them.
"Error Details: The Jetpack server was unable to communicate with your site [IXR -32300: transport error: http_request_failed Operation timed out after 15001 milliseconds with 0 bytes received]"
Your host is limiting concurrent PHP connections. Jetpack needs to be able to talk and receive at the same time, which means it needs concurrent PHP processes. Most commonly, asking your host to change the PHP_FCGI_CHILDREN setting to 2 will solve this issue.
string(60) "-32301: transport error – HTTP status code was not 200 (500)"
This is a server-side error from your web host. Check your PHP error log (or ask your host to) to see if there are any notices from around the time this error showed up.
This error is possibly a misconfiguration in lighttpd. There are some suggestions at this forum thread: “JetPack Instl issue with SSL and lighttpd“.
In a misconfigured site, both URLs will show “XML-RPC server accepts POST requests only.”