Why my Facebook counters show 0 even though I do have shares?
Sometimes Facebook caches the counters on their side.
To fix it, please use Facebook Developer section: https://developers.facebook.com/
Enter your website's URL there and press Debug. On this page you willl see all the data from the Facebook cache. If you think they should be updated, simply press "Scrape Again". Then refresh your website with ctrl+f5 to see changes.