This seems to be a common problem with the update to 3.8. Posting to Facebook does not work, and disconnect/reconnect does not help. I also tried deactivating/reactivating Jetpack. The problem began as soon as I updated to WordPress 3.8.
I have also noticed that the "Publicize" widget is also not placing sharing buttons on my blog either, though I've tried to get that to work also.
My blog site is http://www.limulussystems.com/blog/ if that helps solve the problem.