How to use metatag:image_src to share images on Facebook using the Service links module?
Try the approach suggested in Comment nr 1 of Issue nr 2387519, which is like so:


Install module Metatag (easy to understand module). Use the module and make your configurations.
Clear the cache.
Go to https://developers.facebook.com/tools/debug/og/object and click the "Fetch new scrape information" button to ping/update your meta tags to Facebook server.