I have a WordPress install in Network mode, with subdomains.
sitex.example.com is displaying a white page, with nothing in the source code.
Other network sites display fine.
I renamed the theme the site was using, but it didn’t pick up Twenty Twelve in response.
A server response checker showed that the site is producing a 200 response code.
I went into Network Admin, and renamed sitex to sitey, but sitey.example.com produced a blank page also.
I checked .htaccess, and it contains the following code:
RewriteEngine On
RewriteBase /
RewriteRule ^index.php$ - [L]
# uploaded files
RewriteRule ^files/(.+) wp-includes/ms-files.php?file=$1 [L]
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule . index.php [L]
I went into my hosting cPanel, and confirmed I still have my wildcard subdomain, and I don’t have a manual subdomain for sitex in cPanel.
I went back into Network Admin, and altered the settings of the site, and set Template & Stylesheet to twentytwelve, but this made no difference.
I’m lost.
I don’t know what else could be causing this.
Do you?
UPDATE
If I turn debugging on, I receive the following:
Warning: include(/…/wp-content/advanced-cache.php)
[function.include]: failed to open stream: No such file or directory
in /wp-settings.php on line 65Warning: include() [function.include]: Failed opening
‘/…/wp-content/advanced-cache.php’ for inclusion
(include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /wp-settings.php
on line 65Notice: wpdb::escape is deprecated since version 3.6! Use
wpdb::prepare() or esc_sql() instead. in
/…/wp-includes/functions.php on line 2913Warning: session_start() [function.session-start]: Cannot send session
cache limiter – headers already sent (output started at
/…/wp-settings.php:65) in
/…/wp-content/plugins/nivo-slider/nivo-slider.php
on line 10
The .htaccess does not have the information for caching so clear cache, network deactivate your caching plugin as well as the nivo slider plugin. If present, remove the setting for enabling caching in wp-config too.
Does /wp-admin.php load for that blog at this point?
If not, using phpmyadmin go into wp_blogid_options to see what is being loaded. You can clear those options and see if the blog loads.
Disable the Nivo Slider plugin to confirm that this is the source of the session_start error. This would definitely cause a white page. I’m looking at the plugin’s source and there is no session_start function, so that’s a bit odd. Is your plugin up to date?
As the error says “headers already sent (output started at /…/wp-settings.php:65)”. This leads me to believe there is a cached instance of session_start that is causing a conflict. Hopefully, solving the issue with session start will allow you to keep using cache if that is functioning properly.
Session Start
The session_start function must run before any other code. Specifically, it must run before the DOCTYPE and other header info is served. The only way I know of running session_start through WordPress is to hook to init (or admin_init if your plugin runs in the admin CP).
add_action('init', 'your_session_starting_function');Another plugin using the init hook could cause a conflict if it runs before your session start.
Troubleshooting Cache Errors
Check your wp-config.php and, if it exists, disable or remove the line
define( 'WP_CACHE', true );. Don’t just set it to false.If you are using a cache plugin like wp-cache, make sure to disable cache.
If you are using a minify plugin, disable minification.
I network disabled a bunch of plugins. These plugins were running on the problem site. After this the problem disappeared.