If Rapid Cache does not appear to be working see Verify if Rapid Cache is working , this article will give you a few suggestions for what to check.

To rule out plugin or theme conflicts, we always recommend Testing Rapid Cache in a Clean WordPress Installation.

If you're having issues running Rapid Cache, a good first step is to verify that you're not running any of these plugins, which have been known to cause problems:

• Force Gzip - Force Gzip uses ob_gzhandler(), which Rapid Cache is not compatible with. Rapid Cache is not compatible with output buffers that attempt to pre-compress HTML output.
• CSS-JS-Booster - CSS-JS-Booster uses ob_gzhandler(), which Rapid Cache is not compatible with. Rapid Cache is not compatible with output buffers that attempt to pre-compress HTML output.
• Mobble - Mobble provides conditional functions for detecting a variety of mobile devices & tablets. However, since Rapid Cache generates caches using PHP Output Buffering, once a cache is generates no PHP functions on that page will be evaluated until the cache is regenerated. If you must use Mobble, you can exclude mobile User-Agents from being cached by Rapid Cache (see "Mobile Themes" below).
• Plainview Activity Monitor - We have had reports of this plugin possibly causing issues with the cache clearing every time the WordPress Dashboard is accessed. See this issue for more details.
• Remove WPMU Dashboard Notification Nag - When this plugin is active, the Rapid Cache plugin will fail to activate.

Some plugins strip the HTML Comments from the source of your pages to minify and compress the size of your HTML pages. While these plugins may not conflict with Rapid Cache, they would have the side effect of hiding the HTML Notes that added by Rapid Cache, which would make it appear as though Rapid Cache is not running.

Common culprits are any plugin related to minifying, compressing, or optimizing HTML. Services like CloudFlare also have options for minifying HTML, which strips out the HTML Comments added by Rapid Cache (see the CloudFlare section below).

Please try disabling any plugins related to minifying or compressing HTML and see if the Rapid Cache HTML notes at the bottom of the source show up.

You can only have one WordPress caching plugin enabled at a time. Please make sure that Rapid Cache is the only caching plugin active.

If you were using or testing other caching plugins, make sure that your .htaccess file does not contain any remnants from those other plugins, as many plugins don't properly clean up after themselves when deactivated.

Also, all caching plugins are required to use the same wp-content/advanced-cache.php file to hook into WordPress for caching. Since all caching plugins use the same file, it's possible another plugin wrote content to that file and is now somehow preventing Rapid Cache from updating it.

You can make sure that Rapid Cache is the only plugin using the advanced-cache.php file by deactivating all other caching plugins, removing define('WP_CACHE', TRUE); from the top of your wp-config.php file (if it exists) and then deleting the wp-content/advanced-cache.php file. Once you've deleted the file, you can disable and then enable Rapid Cache (in Dashboard → Rapid Cache → Plugin Options → Enable/Disable) to have it rewrite the advanced-cache.php file.

As a last-resort, you can try manually uninstalling Rapid Cache and then reinstalling it.

Rapid Cache supports the Nginx web server. If you're having issues, here are a few things to try:

• If you have Zlib compression enabled, try disabling it.

See also: Recommended Nginx Configuration for Rapid Cache