Problems connecting your WordPress site to Jetpack.
XML-RPC server accepts POST requests only
After setting up a fresh install of WordPress on my Digital Ocean box I had a few issues reconnecting my Jetpack accounts.
I got the error ‘XML-RPC server accepts POST requests only’ and after doing some research found out it’s caused by a missing PHP extension for XML that handles Dom activities.
sudo apt-get install php-xml
After installing and restarting my server the problem was resolved. One thing the docs didn’t mention was the fact that the extension was or could be missing.