how load wordpress in a subdirectory without wordpress in root directory taking over
<p>I have my production Wordpress website at <code>example.com.au</code> running from <code>/public_html</code></p>

<p>I also have a standalone Wordpress site in a <code>/public_html/mainwp</code> subdirectory running <a href="http://www.mainwp.com" rel="nofollow">Main WP</a>.</p>

<p>The <code>.htaccess</code> in <code>/public_html</code> is:</p>

<pre><code># Begin Wordpress
&lt;IfModule mod_rewrite.c&gt;
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]
&lt;/IfModule&gt;
# End Wordpress
</code></pre>

<p>If I try to load <code>example.com.au/mainwp/wp-admin</code>, I receive a 404 served by Wordpress at <code>example.com.au</code></p>

<p>If I rename <code>/public_html/.htaccess</code> to <code>.htaccess.temp</code>, <code>example.com.au/mainwp/wp-admin</code> loads fine.</p>

<p>Something changed over the weekend and I can't work out what. I'm quite sure this <code>.htaccess</code> was working before the weekend.</p>

<p>Help appreciated.</p>

<p><strong><em>Update</em></strong>: From Sagar's answer, I've confirmed <code>/public_html/mainwp/.htaccess</code> contains the following code:</p>

<pre><code># BEGIN WordPress
&lt;IfModule mod_rewrite.c&gt;
RewriteEngine On
RewriteBase /mainwp/
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /mainwp/index.php [L]
&lt;/IfModule&gt;
# END WordPress
</code></pre>

<p>and previously that situation was working, but now it is not: <code>example.com.au/mainwp/wp-admin</code> delivers a 404 served by Wordpress at <code>example.com.au</code></p>