This will happen if the post is already published, or if Publicize thinks it’s been published in the past.
If you experience issues when editing drafts as well, could you try to reset your connections, as explained here:
http://jetpack.me/support/publicize/google/#reconnecting-google
http://jetpack.me/support/publicize/facebook/#reconnecting-facebook
http://jetpack.me/support/publicize/twitter/#reconnecting-twitter
If that doesn’t help, can you please use Jetpack’s Debugger module to send us some more information about your site?
1) Go to the Jetpack page in your dashboard.
2) Click on the Debug link appearing at the bottom of the page.
3) Click the link that says “click here to contact Jetpack support.”
4) Fill in the description box and your name and email address.
5) Click the “Contact Support” button.
Thanks!