I am also having issue with Publicize.
No error message. It simply does not send anything.
I disabled all other plugins to test conflicts. No improvement.
Contacted Jetpack support about 2 days ago. No response.
xmlrppc is accessible
No caching on site at the moment. No CDN.
It worked few days ago. I changed absolutely nothing. Simply publicized one post, then next post, around 20 minuutes later, it did not, and then past two days its dead in water.
As last thing I went and got Jetpack Beta Master, updated to Bleeding Edge, manually. No improvement to situation.