I'm running a dedicated server and I have double checked to ensure that mod_deflate is enabled via Apache (which it is).
I've also gone in under cPanel > Site Optimization, and turned on compression.
The site is running WordPress with the W3 Total Cache Plugin and the GZip options enabled. Sure enough when I check the page response headers in Google Chrome's PageSpeed plugin there is no 'Content-Encoding: gzip' header. I've also ran the site though the GZip checker but it says compression is not enabled anyways.
I am not sure what's causing the compression not to work. It's enabled on the server which I have verified through my Linux System Administrators at Host. Any ideas?
[edited by: Ocean10000 at 5:30 am (utc) on Mar 29, 2013] [edit reason] Removed links [/edit]
Before anything else: Dump ALL the "IfModule..." envelopes. Not their content, just the envelopes themselves. Those are boilerplate that comes with mass distributions. You are now on an individual server that either has or does not have the required modules.
Once you've dumped the envelopes you will have a clearer idea of what your overall structure is.
Besides, nesting "If" statements makes me nervous. The more complicated you get, the more room there is for unintended consequences. (See unrelated thread elsewhere about surprising discoveries involving the humble FilesMatch.)