The default WordPress rewrite rules for permalinks might not work in some cases. For example, when you have other settings defined in .htaccess files located in subfolders.

To exclude the subfolders from the WordPress rewrite rules, you need to edit the .htaccess file and change the bold line below:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

to

RewriteRule ./ /index.php [L]