404 error with .php page templates

Hey everyone.

I’m using WP 2.86 and having issues with ‘pretty permalinks’. I’m using /%year%/%monthnum%/%postname%/ and I get a 404 page not found error for any new .php page I try and add in to my template. In this particular instance I’d created a ‘categories.php’ page in which to call wp_list_categories and it keeps telling me the page doesn’t exist. A guestbook_template.php also came with the theme I’m working on and it gets a 404 not found as well.

I’ve deactivated all plugins, still doesn’t work. Set all permalinks to default ‘ugly’, still doesn’t work.
My settings > permalinks doesn’t have any mention of .htaccess in there.

.htaccess currently reads as

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

# END WordPress

I don’t have access to the httpd.config file, nor will my host allow it, so I can’t check if Allowoverride is set to ‘all’ or ‘none’, as this seems to be the general issue.

Basically, is there anything I’ve missed, or anything else I can try?

Thanks!