As @luke mentioned above, we’re looking into the issue. It appears Facebook made a significant change to their API today, thus causing issues with many Facebook sharing plugins.
We can restore this functionality in Jetpack, and we’re working as hard as we can to roll out a fix for this in the next version of Jetpack: https://github.com/Automattic/jetpack/pull/4879
For now, you can get share counts from Facebook by switching to the Official Buttons style at Settings -> Sharing in your Dashboard, or if you wish to just disable share counts on all of the Icon Only and Icon + Text button styles, please follow this guide: https://jeremy.hu/jetpack-remove-the-share-counts-from-the-sharing-buttons/