Hi Tuan,
The EB thumbs image uploads images with a space in the name. Although that in itself is not a problem, Facebook does not recognise the og:image tag if there is a space in the name. Could you add that the eb thumb adds an _ instead of a space?
That would solve it,
Bye
Tim
(if the code is easy to change than giving me the code is also easy. My customers are not understanding why the link image works sometimes and sometimes not)