Thanks Bernie. We had another close look. If count shows 0, then it can be a result of two things:
1.) Our limit to retrieve counts is exhausted for that day (in this free plugin all users share the same Facebook app which has a daily limit of calls it can make to Facebook servers, so if for that day the limit has been reached, it will return 0. In this plugin https://www.ultimatelysocial.com/usm-premium/ users can set up their own Facebook app (easily), so they don’t have to share the limits with others).
– or –
2.) Your server is not able to call the Facebook server due to issues (e.g. it might be an SSL issue or wp_remote_post calls are not going through from your server)
It sounds very much like the issue is no.2, so please have this checked with your server team or hosting company.