Hello, is this normal. that no preview photo will show if I share a link? In wordpress there is a preview photo available.
Screenshot: http://imgur.com/a/4BYXg
Maybe something wrong with you picture, you have to follow rule of facebook image size.
Easily you can check post preview on facebook using this tool.
What does this mean?
The og: image property should be specified explicitly, even if a value can be derived from other tags.