I'm unsure why Social Debug isn't scanning your page properly. However, the tags are being set and are detected by Facebook itself:
developers.facebook.com/tools/debug/og/o...rshack.co.uk%2Fforum
To overwrite the tags on any specific page, you'd need to add the following output to the page:
{SCOpenGraph title=Best Title for this Page}
{SCOpenGraph descripton=Best description for this page}
{SCOpenGraph image=https://domain.com/link-to-image-for-this-page.jpg}JFBConnect will detect those tags and use them in place of the tags that it would normally automatically generate.
There isn't a specific file in JFBConnect you should edit to do this.. it should be on the layout pages for PHPBB (or your bridge).
I hope that helps explain, but if you have any questions, just let me know.
Thanks,
Alex