I know this issue was resolved, but for anyone else who has this problem that the above solution doesn't resolve, I may have another answer.
This was happening to me even with no plugins active. The cause of the problem was having the Ghostery browser plugin active (Note: browser plugin, not Wordpress plugin), which blocks ad networks, behavioural data providers, and any companies interested in your activity. In your case, it may not be Ghostery but a similar browser plugin.
After disabling Ghostery, all the sharing buttons appeared.
Hope that helps.