I know this topic has been covered a lot; however, I do have a custom .htaccess rule and when I tried to add the below for my 404 custom page, it didn't work and start showing Not found page:
ErrorDocument 404/foldername/error/404.php
My .htaccess rules are as below:
RewriteEngine On
RewriteBase /
# Redirect non-www to www
RewriteCond %{HTTP_HOST} !^www\.culture-insider\.com$
RewriteRule (.*) https://www.culture-insider.com/$1 [R=301,L]
# Internal rewrite for pages
RewriteRule ^([-a-zA-Z0-9]+)$ index.php?page=$1 [L]
Is there a specific rule that I need to add to show my 404.php custom page or are any changes needed?