Zdravím, mám stejný problém, ale povolení POST bohužel nepomohlo.

Your Jetpack has a glitch. We’re sorry for the inconvenience. Please try again later, if the issue continues please contact support with this message: xml_rpc-32700
Try connecting again.
Detaily chyby: The Jetpack server could not communicate with your site's XML-RPC URL. Please check to make sure http://u-nudle.cz/xmlrpc.php is working properly. It should show 'XML‑RPC server accepts POST requests only.' on a line by itself when viewed in a browser and should not have any blank links or extra output anywhere.