How have you changed the URL? Have you also changed the page slug of forum? Just edit the forum page and check the page slug. It recommended to be the same. Also please make sure you have one forum page and there is no other pages with [wpforo] shortcode.
Please disable "Turn WordPress to wpForo" option shown in your screenshot. Don't use that option, it disables all pages and posts of WordPress on front-end. If you want to set wpForo on home page use the correct way explained here (you should have two forum pages, second one should be set as home in WP settings):
Please navigate to Dashboard > Forums > Settings > general Tab and change the /recent/ path to something like /recent-posts/ or so.Delete all caches and test it again with new browser. Call the recent page with new URL not with the old /recent/ URL.
It seems you have a page, post or category with the same slug/path and they conflict with each other.