Why Do My Facebook Counters Show 0 Though I Do Have These Shares?
Sometimes Facebook caches the counters on their side.
To fix it, do to the Facebook Developer section: https://developers.facebook.com/
Enter your website URL there and click "Debug". On the page that will open, you will see all the data from the Facebook cache. If you want to update them, click "Scrape Again". Then refresh your website with ctrl+f5 to see the changes.