Have you run your url through the url linter tool? [developers.facebook.com...] Sometimes this forces facebook to crawl your site and fix these errors. Other times I've noticed this is just down to allowing time for them to crawl it.
great works a treat, I think it was because I placed the facebook post behind comment post. I have now placed on the pre post also and works well. Thank you. Is there anyway I can add parameters into the message?