Menu Broken, not fixed when plugin removed

I tried this plugin out but once activated, my menus broke. For example, one menu items goes to /calendar, but it doesn’t work because the url is now /calendar.php. I deactivated, then uninstalled the plugin but this behaviour remains, all of my pages have the .php extension. How can this be fixed? I assumed removing the plugin would fix it but no luck. My page is located at http://ntmcpr.normcopeland.com

https://ww.wp.xz.cn/plugins/php-code-for-posts/