How to delete a complete forum topic from root folder in wordpress

To troubleshoot why “Bin” is not working, you’ll likely need to contact the plugin author. If it’s your own custom plugin/theme/code, please share above and perhaps we can be of more assistance.

Another option might be to close the forum. Again you would need to contact the author to determine whether that is possible or not with the current codebase.

An alternative, manual way to delete the forum would be to use phpMyAdmin to directly edit your database. Be sure to save a backup first, and be sure you understand the structure saved in the database. From your screenshot it appears that a “forum” is simply a custom post type but it’s possible that it’s more complex than that. If it’s a CPT and you hover your cursor over “edit” you should be able to see the post ID in the target URL. You can then log into phpMyAdmin, go to the (prefix)_posts table (i.e. wp_posts), search for that post ID, and manually delete it. You may then want to use a database optimization plugin which can delete all of that post’s orphaned revisions and postmeta, but this would at least remove the post completely.