I have checked manually an older post with my facebook conexion in the Publizice box beside the post, but it does not appear in my facebook page.
Updating a post in any way i-e changing its date does not make it to share on any social media.
Besides your WordPress app might be non functioning or inactive at that time though apparently looking active (one of the major issues of Facebook integeration.)
Maybe I am not doing the manual proceedure correctly
No manual procedure required, you just have to connect your blog to Facebook via WordPress app. As I told above the app sometimes seems connected but it doesn't share your posts. All you have to do is to reconnect it.
(I prefer sharing manually rather than connecting it again and again).
Hope you got the point now.