I figured out that the permanent link structure is not working:
All links to current page are changing to "./" No permalink contains the full url including the domain.
I checked all the theme's relevant files, searched for "./" in the theme directory in notepad++ to no avail.
If it's probably not the theme, then what is changing the urls? I even disabled all cache and minify plugins in vain.
Please help
Oh this has been solved beautifully!
There was a criminal plugin which I forgot to deactivate: WP-HTML-Compression by Steven Vachon
It was reducing all the permalinks to relative links and then modifying all links which connect to the current page rendering facebook unable to find out the link of the page on which it is hosted.
So I deleted the plugin, and it's working all fine.