FATAL ERROR: Unable to find the uk-english or english language directories. Please notify the administrator.
The error message is quite clear, UBB.threads cannot find the "english" or "uk-english" language directories, which would be /forum/languages for your site.
Have you (or has your host, without telling you, which actually happens more than you'd think) changed servers recently? Or moved your forum to a different folder? Are the paths in your /forum/includes/config.inc.php file all correct?
I'm looking at your forums now though, and they seem to be working fine:
https://www.outdoorking.com/forum/ubbthreads.php?ubb=cfrm